diff --git a/Package.resolved b/Package.resolved
new file mode 100644
index 0000000..7ee2c42
--- /dev/null
+++ b/Package.resolved
@@ -0,0 +1,16 @@
+{
+  "object": {
+    "pins": [
+      {
+        "package": "ObjectCoder",
+        "repositoryURL": "https://github.com/g-Off/ObjectCoder.git",
+        "state": {
+          "branch": null,
+          "revision": "701d70d41d065b7b6567094a45bd4b796f4eb4d2",
+          "version": "0.1.0"
+        }
+      }
+    ]
+  },
+  "version": 1
+}
diff --git a/Package.swift b/Package.swift
index 080ef1d..c6bc9ec 100644
--- a/Package.swift
+++ b/Package.swift
@@ -13,11 +13,12 @@ let package = Package(
             targets: ["XcodeProject"]),
     ],
     dependencies: [
+		.package(url: "https://github.com/g-Off/ObjectCoder.git", .exact("0.1.0"))
     ],
     targets: [
         .target(
             name: "XcodeProject",
-            dependencies: []),
+            dependencies: ["ObjectCoder"]),
         .testTarget(
             name: "XcodeProjectTests",
             dependencies: ["XcodeProject"]),
diff --git a/Sources/XcodeProject/Archiving/Encoder/AnyCodingKey.swift b/Sources/XcodeProject/Archiving/Encoder/AnyCodingKey.swift
index d73a6ce..534397e 100644
--- a/Sources/XcodeProject/Archiving/Encoder/AnyCodingKey.swift
+++ b/Sources/XcodeProject/Archiving/Encoder/AnyCodingKey.swift
@@ -21,6 +21,10 @@ struct AnyCodingKey: CodingKey, Equatable, Hashable {
 		self.intValue = intValue
 	}
 	
+	init(index: Int) {
+		self.init(intValue: index)!
+	}
+	
 	init<Key>(_ base: Key) where Key: CodingKey {
 		if let intValue = base.intValue {
 			self.init(intValue: intValue)!
diff --git a/Sources/XcodeProject/Archiving/Encoder/PBXEncoder.swift b/Sources/XcodeProject/Archiving/Encoder/PBXEncoder.swift
index 86b98ab..9520f9f 100644
--- a/Sources/XcodeProject/Archiving/Encoder/PBXEncoder.swift
+++ b/Sources/XcodeProject/Archiving/Encoder/PBXEncoder.swift
@@ -6,16 +6,38 @@
 //
 
 import Foundation
+import ObjectCoder
 
 class PBXObjectEncoder {
 	static let objectVersionKey = CodingUserInfoKey(rawValue: "objectVersion")!
 	var objectVersion: ObjectVersion = .xcode93
 	
+	private static func quotedKey(_ codingKeys: [CodingKey]) -> CodingKey {
+		let codingKey = codingKeys.last!
+		if codingKey.intValue != nil { return codingKey }
+		return AnyCodingKey(stringValue: codingKey.stringValue.quotedString)!
+	}
+	
 	func encode(_ object: PBXObject) throws -> [String: AnyObject] {
-		let encoder = _PBXObjectEncoder()
-		encoder.userInfo = [PBXObjectEncoder.objectVersionKey: objectVersion]
+		let options = ObjectEncoder<NSObject>.Options(
+			keyEncodingStrategy: .custom(PBXObjectEncoder.quotedKey),
+			userInfo: [PBXObjectEncoder.objectVersionKey: objectVersion]
+		)
+		let boxer = ObjectEncoder<NSObject>.Boxer()
+		boxer.addWrapper { (object: PBXObject) -> NSObject in
+			return NSString(string: object.plistID.description)
+		}
+		boxer.encodedString = { (value, _) in
+			return NSString(string: value.quotedString)
+		}
+		let encoder = ObjectEncoder(options: options, boxer: boxer)
 		try object.encode(to: encoder)
-		return encoder.storage.popContainer() as? [String: AnyObject] ?? [:]
+		return encoder.encoded as? [String: AnyObject] ?? [:]
+		
+//		let encoder = _PBXObjectEncoder()
+//		encoder.userInfo = [PBXObjectEncoder.objectVersionKey: objectVersion]
+//		try object.encode(to: encoder)
+//		return encoder.storage.popContainer() as? [String: AnyObject] ?? [:]
 	}
 }
 
diff --git a/Sources/XcodeProject/Archiving/Encoder/_PBXObjectEncoder+KeyedContainer.swift b/Sources/XcodeProject/Archiving/Encoder/_PBXObjectEncoder+KeyedContainer.swift
index a795580..b85501a 100644
--- a/Sources/XcodeProject/Archiving/Encoder/_PBXObjectEncoder+KeyedContainer.swift
+++ b/Sources/XcodeProject/Archiving/Encoder/_PBXObjectEncoder+KeyedContainer.swift
@@ -28,17 +28,17 @@ extension _PBXObjectEncoder.KeyedContainer: KeyedEncodingContainerProtocol {
 	}
 	
 	func encodeNil(forKey key: Key) throws {
-		container[key.stringValue] = NSNull()
+		container[key.stringValue.quotedString] = NSNull()
 	}
 	
 	func encode(_ value: String, forKey key: Key) throws {
-		container[key.stringValue] = NSString(string: value.quotedString)
+		container[key.stringValue.quotedString] = NSString(string: value.quotedString)
 	}
 	
 	func encode<T>(_ value: T, forKey key: Key) throws where T: Encodable {
 		encoder.codingPath.append(key)
 		defer { encoder.codingPath.removeLast() }
-		container[key.stringValue] = try encoder.box(value)
+		container[key.stringValue.quotedString] = try encoder.box(value)
 	}
 	
 	func nestedContainer<NestedKey>(keyedBy keyType: NestedKey.Type, forKey key: Key) -> KeyedEncodingContainer<NestedKey> where NestedKey: CodingKey {
diff --git a/Sources/XcodeProject/Archiving/PropertyList.swift b/Sources/XcodeProject/Archiving/PropertyList.swift
index 419260f..bd6ab11 100644
--- a/Sources/XcodeProject/Archiving/PropertyList.swift
+++ b/Sources/XcodeProject/Archiving/PropertyList.swift
@@ -21,6 +21,11 @@ struct PropertyList {
 		return PropertyList(value)
 	}
 	
+	subscript(key: CodingKey) -> PropertyList? {
+		guard let dictionary = self.dictionary else { return nil }
+		return PropertyList(dictionary[key.stringValue])
+	}
+	
 	private func getTypedObject<T>() -> T? {
 		return object as? T
 	}
diff --git a/Sources/XcodeProject/Objects/Build Phases/PBXBuildPhase.swift b/Sources/XcodeProject/Objects/Build Phases/PBXBuildPhase.swift
index f89c840..e1843ea 100644
--- a/Sources/XcodeProject/Objects/Build Phases/PBXBuildPhase.swift	
+++ b/Sources/XcodeProject/Objects/Build Phases/PBXBuildPhase.swift	
@@ -6,7 +6,7 @@
 //  Copyright © 2017 Geoffrey Foster. All rights reserved.
 //
 
-public class PBXBuildPhase: PBXObject {
+public class PBXBuildPhase: PBXProjectItem {
 	private enum CodingKeys: String, CodingKey {
 		case name
 		case files
@@ -61,18 +61,18 @@ public class PBXBuildPhase: PBXObject {
 	override func update(with plist: PropertyList, objectCache: ObjectCache) {
 		super.update(with: plist, objectCache: objectCache)
 		
-		guard let files = plist["files"]?.array else {
+		guard let files = plist[CodingKeys.files]?.array else {
 			fatalError()
 		}
-		self._name = plist["name"]?.string
+		self._name = plist[CodingKeys.name]?.string
 		self.files = files.compactMap {
 			let file: PBXBuildFile? = objectCache.object(for: PBXGlobalID(rawValue: $0))
 			return file
 		}
 		
-		self.runOnlyForDeploymentPostprocessing = plist["runOnlyForDeploymentPostprocessing"]?.bool
+		self.runOnlyForDeploymentPostprocessing = plist[CodingKeys.runOnlyForDeploymentPostprocessing]?.bool
 		
-		if let v = plist["buildActionMask"]?.string, let buildActionMask = Int32(v) {
+		if let v = plist[CodingKeys.buildActionMask]?.string, let buildActionMask = Int32(v) {
 			self.buildActionMask = buildActionMask
 		}
 	}
diff --git a/Sources/XcodeProject/Objects/Build Phases/PBXCopyFilesBuildPhase.swift b/Sources/XcodeProject/Objects/Build Phases/PBXCopyFilesBuildPhase.swift
index a4addf3..074301b 100644
--- a/Sources/XcodeProject/Objects/Build Phases/PBXCopyFilesBuildPhase.swift	
+++ b/Sources/XcodeProject/Objects/Build Phases/PBXCopyFilesBuildPhase.swift	
@@ -39,9 +39,9 @@ public final class PBXCopyFilesBuildPhase: PBXBuildPhase {
 	
 	override func update(with plist: PropertyList, objectCache: ObjectCache) {
 		super.update(with: plist, objectCache: objectCache)
-		guard let dstPath = plist["dstPath"]?.string else { fatalError() }
+		guard let dstPath = plist[CodingKeys.dstPath]?.string else { fatalError() }
 		self.dstPath = dstPath
-		guard let dstSubfolderSpec = Destination(string: plist["dstSubfolderSpec"]?.string) else { fatalError() }
+		guard let dstSubfolderSpec = Destination(string: plist[CodingKeys.dstSubfolderSpec]?.string) else { fatalError() }
 		self.dstSubfolderSpec = dstSubfolderSpec
 	}
 	
diff --git a/Sources/XcodeProject/Objects/Build Phases/PBXShellScriptBuildPhase.swift b/Sources/XcodeProject/Objects/Build Phases/PBXShellScriptBuildPhase.swift
index 2f74255..05c550d 100644
--- a/Sources/XcodeProject/Objects/Build Phases/PBXShellScriptBuildPhase.swift	
+++ b/Sources/XcodeProject/Objects/Build Phases/PBXShellScriptBuildPhase.swift	
@@ -27,13 +27,13 @@ public final class PBXShellScriptBuildPhase: PBXBuildPhase {
 	
 	override func update(with plist: PropertyList, objectCache: ObjectCache) {
 		super.update(with: plist, objectCache: objectCache)
-		self.inputPaths = plist["inputPaths"]?.array ?? []
-		self.outputPaths = plist["outputPaths"]?.array ?? []
-		self.inputFileListPaths = plist["inputFileListPaths"]?.array ?? []
-		self.outputFileListPaths = plist["outputFileListPaths"]?.array ?? []
-		self.shellPath = plist["shellPath"]?.string
-		self.shellScript = plist["shellScript"]?.string
-		self.showEnvVarsInLog = plist["showEnvVarsInLog"]?.bool
+		self.inputPaths = plist[CodingKeys.inputPaths]?.array ?? []
+		self.outputPaths = plist[CodingKeys.outputPaths]?.array ?? []
+		self.inputFileListPaths = plist[CodingKeys.inputFileListPaths]?.array ?? []
+		self.outputFileListPaths = plist[CodingKeys.outputFileListPaths]?.array ?? []
+		self.shellPath = plist[CodingKeys.shellPath]?.string
+		self.shellScript = plist[CodingKeys.shellScript]?.string
+		self.showEnvVarsInLog = plist[CodingKeys.showEnvVarsInLog]?.bool
 	}
 	
 	public override func encode(to encoder: Encoder) throws {
diff --git a/Sources/XcodeProject/Objects/PBXBuildFile.swift b/Sources/XcodeProject/Objects/PBXBuildFile.swift
index 8e86ef1..78f1d73 100644
--- a/Sources/XcodeProject/Objects/PBXBuildFile.swift
+++ b/Sources/XcodeProject/Objects/PBXBuildFile.swift
@@ -6,10 +6,11 @@
 //  Copyright © 2017 Geoffrey Foster. All rights reserved.
 //
 
-public final class PBXBuildFile: PBXObject {
+public final class PBXBuildFile: PBXProjectItem {
 	private enum CodingKeys: String, CodingKey {
 		case fileRef
 		case settings
+		case productRef
 	}
 	public enum Attribute: String, Comparable, Encodable {
 		public static func < (lhs: PBXBuildFile.Attribute, rhs: PBXBuildFile.Attribute) -> Bool {
@@ -18,6 +19,7 @@ public final class PBXBuildFile: PBXObject {
 		
 		case `public` = "Public"
 		case `private` = "Private"
+		case required = "Required"
 		case `weak` = "Weak"
 		case client = "Client"
 		case server = "Server"
@@ -61,6 +63,8 @@ public final class PBXBuildFile: PBXObject {
 	}
 	var settings: Settings?
 	
+	private(set) var productReference: PBXProductDependency?
+	
 	public convenience init(globalID: PBXGlobalID, fileReference: PBXReference) {
 		self.init(globalID: globalID)
 		fileRef = fileReference
@@ -71,24 +75,27 @@ public final class PBXBuildFile: PBXObject {
 		var container = encoder.container(keyedBy: CodingKeys.self)
 		try container.encodeIfPresent(fileRef, forKey: .fileRef)
 		try container.encodeIfPresent(settings, forKey: .settings)
+		try container.encodeIfPresent(productReference, forKey: .productRef)
 	}
 	
 	override func update(with plist: PropertyList, objectCache: ObjectCache) {
 		super.update(with: plist, objectCache: objectCache)
-		self.fileRef = objectCache.object(for: PBXGlobalID(rawValue: plist["fileRef"]?.string))
+		self.fileRef = objectCache.object(for: PBXGlobalID(rawValue: plist[CodingKeys.fileRef]?.string))
+		self.productReference = objectCache.object(for: PBXGlobalID(rawValue: plist[CodingKeys.productRef]?.string))
 		self.settings = Settings(plist["settings"]?.dictionary)
 	}
 	
 	override var archiveComment: String {
-		guard let fileRef = fileRef, let parent = parent else {
+		guard let parent = parent, let refComment = fileRef?.archiveComment ?? productReference?.archiveComment else {
 			return super.archiveComment
 		}
-		return "\(fileRef.archiveComment) in \(parent.archiveComment)"
+		return "\(refComment) in \(parent.archiveComment)"
 	}
 	
 	override func visit(_ visitor: ObjectVisitor) {
 		super.visit(visitor)
 		visitor.visit(object: fileRef)
+		visitor.visit(object: productReference)
 	}
 	
 	override var archiveInPlistOnSingleLine: Bool {
diff --git a/Sources/XcodeProject/Objects/PBXBuildRule.swift b/Sources/XcodeProject/Objects/PBXBuildRule.swift
index c306db4..6636ed0 100644
--- a/Sources/XcodeProject/Objects/PBXBuildRule.swift
+++ b/Sources/XcodeProject/Objects/PBXBuildRule.swift
@@ -6,7 +6,7 @@
 //  Copyright © 2017 Geoffrey Foster. All rights reserved.
 //
 
-public final class PBXBuildRule: PBXObject {
+public final class PBXBuildRule: PBXProjectItem {
 	private enum CodingKeys: String, CodingKey {
 		case compilerSpec
 		case fileType
@@ -22,11 +22,11 @@ public final class PBXBuildRule: PBXObject {
 	
 	override func update(with plist: PropertyList, objectCache: ObjectCache) {
 		super.update(with: plist, objectCache: objectCache)
-		self.compilerSpec = plist["compilerSpec"]?.string
-		self.fileType = plist["fileType"]?.string
-		self.isEditable = plist["isEditable"]?.bool ?? true
-		self.outputFiles = plist["outputFiles"]?.array ?? []
-		self.script = plist["script"]?.string
+		self.compilerSpec = plist[CodingKeys.compilerSpec]?.string
+		self.fileType = plist[CodingKeys.fileType]?.string
+		self.isEditable = plist[CodingKeys.isEditable]?.bool ?? true
+		self.outputFiles = plist[CodingKeys.outputFiles]?.array ?? []
+		self.script = plist[CodingKeys.script]?.string
 	}
 	
 	public override func encode(to encoder: Encoder) throws {
diff --git a/Sources/XcodeProject/Objects/PBXContainerItem.swift b/Sources/XcodeProject/Objects/PBXContainerItem.swift
new file mode 100644
index 0000000..0b6ea3b
--- /dev/null
+++ b/Sources/XcodeProject/Objects/PBXContainerItem.swift
@@ -0,0 +1,16 @@
+//
+//  PBXContainerItem.swift
+//  
+//
+//  Created by Geoffrey Foster on 2019-07-03.
+//
+
+import Foundation
+
+public class PBXContainerItem: PBXObject {
+	
+}
+
+public class PBXProjectItem: PBXContainerItem {
+	
+}
diff --git a/Sources/XcodeProject/Objects/PBXContainerItemProxy.swift b/Sources/XcodeProject/Objects/PBXContainerItemProxy.swift
index 671a69f..b59b1ad 100644
--- a/Sources/XcodeProject/Objects/PBXContainerItemProxy.swift
+++ b/Sources/XcodeProject/Objects/PBXContainerItemProxy.swift
@@ -6,7 +6,7 @@
 //  Copyright © 2017 Geoffrey Foster. All rights reserved.
 //
 
-final class PBXContainerItemProxy: PBXObject {
+final class PBXContainerItemProxy: PBXContainerItem {
 	private enum CodingKeys: String, CodingKey {
 		case containerPortal
 		case proxyType
@@ -33,10 +33,10 @@ final class PBXContainerItemProxy: PBXObject {
 		super.update(with: plist, objectCache: objectCache)
 		
 		guard
-			let containerPortal = objectCache.object(for: PBXGlobalID(rawValue: plist["containerPortal"]?.string)),
-			let proxyType = ProxyType(string: plist["proxyType"]?.string),
-			let remoteGlobalIDString = plist["remoteGlobalIDString"]?.string,
-			let remoteInfo = plist["remoteInfo"]?.string
+			let containerPortal = objectCache.object(for: PBXGlobalID(rawValue: plist[CodingKeys.containerPortal]?.string)),
+			let proxyType = ProxyType(string: plist[CodingKeys.proxyType]?.string),
+			let remoteGlobalIDString = plist[CodingKeys.remoteGlobalIDString]?.string,
+			let remoteInfo = plist[CodingKeys.remoteInfo]?.string
 			else {
 				fatalError()
 		}
diff --git a/Sources/XcodeProject/Objects/PBXObject.swift b/Sources/XcodeProject/Objects/PBXObject.swift
index a4f2462..505ca13 100644
--- a/Sources/XcodeProject/Objects/PBXObject.swift
+++ b/Sources/XcodeProject/Objects/PBXObject.swift
@@ -25,6 +25,10 @@ public class PBXObject: Encodable {
 		self.globalID = globalID
 	}
 	
+	func awake(from decoder: Decoder) throws {
+		
+	}
+	
 	public func encode(to encoder: Encoder) throws {
 		var container = encoder.container(keyedBy: CodingKeys.self)
 		try container.encode(isa, forKey: .isa)
@@ -129,4 +133,7 @@ let types: [PBXObject.Type] = [
 	XCBuildConfiguration.self,
 	XCConfigurationList.self,
 	XCVersionGroup.self,
+	XCLocalSwiftPackageReference.self,
+	XCRemoteSwiftPackageReference.self,
+	XCSwiftPackageProductDependency.self,
 ]
diff --git a/Sources/XcodeProject/Objects/PBXProductDependency.swift b/Sources/XcodeProject/Objects/PBXProductDependency.swift
new file mode 100644
index 0000000..69807e0
--- /dev/null
+++ b/Sources/XcodeProject/Objects/PBXProductDependency.swift
@@ -0,0 +1,12 @@
+//
+//  PBXProductDependency.swift
+//  
+//
+//  Created by Geoffrey Foster on 2019-07-03.
+//
+
+import Foundation
+
+public class PBXProductDependency: PBXProjectItem {
+	
+}
diff --git a/Sources/XcodeProject/Objects/PBXProject.swift b/Sources/XcodeProject/Objects/PBXProject.swift
index 3ba290d..c839ca1 100644
--- a/Sources/XcodeProject/Objects/PBXProject.swift
+++ b/Sources/XcodeProject/Objects/PBXProject.swift
@@ -17,6 +17,7 @@ public final class PBXProject: PBXObject, PBXContainer {
 		case hasScannedForEncodings
 		case knownRegions
 		case mainGroup
+		case packageReferences
 		case productRefGroup
 		case projectDirPath
 		case projectReferences
@@ -88,6 +89,7 @@ public final class PBXProject: PBXObject, PBXContainer {
 		case xcode8_0 = "Xcode 8.0"
 		case xcode9_3 = "Xcode 9.3"
 		case xcode_10 = "Xcode 10.0"
+		case xcode_11 = "Xcode 11.0"
 	}
 
 	var attributes = Attributes([:])
@@ -115,6 +117,7 @@ public final class PBXProject: PBXObject, PBXContainer {
 			targets.forEach { $0.parent = self }
 		}
 	}
+	var packageReferences: [XCSwiftPackageReference]?
 	
 	var path: String?
 	
@@ -146,18 +149,18 @@ public final class PBXProject: PBXObject, PBXContainer {
 		super.update(with: plist, objectCache: objectCache)
 		
 		guard
-			let attributes = plist["attributes"]?.dictionary,
-			let buildConfigurationListID = PBXGlobalID(rawValue: plist["buildConfigurationList"]?.string),
+			let attributes = plist[CodingKeys.attributes]?.dictionary,
+			let buildConfigurationListID = PBXGlobalID(rawValue: plist[CodingKeys.buildConfigurationList]?.string),
 			let buildConfigurationList = objectCache.object(for: buildConfigurationListID) as? XCConfigurationList,
-			let compatibilityVersion = CompatibilityVersion(rawValue: plist["compatibilityVersion"]?.string ?? ""),
-			let developmentRegion = plist["developmentRegion"]?.string,
-			let hasScannedForEncodings = plist["hasScannedForEncodings"]?.string,
-			let knownRegions = plist["knownRegions"]?.array,
-			let mainGroup = objectCache.object(for: PBXGlobalID(rawValue: plist["mainGroup"]?.string)) as? PBXGroup,
-			let productRefGroup = objectCache.object(for: PBXGlobalID(rawValue: plist["productRefGroup"]?.string)) as? PBXGroup,
-			let projectDirPath = plist["projectDirPath"]?.string,
-			let projectRoot = plist["projectRoot"]?.string,
-			let targets = plist["targets"]?.array
+			let compatibilityVersion = CompatibilityVersion(rawValue: plist[CodingKeys.compatibilityVersion]?.string ?? ""),
+			let developmentRegion = plist[CodingKeys.developmentRegion]?.string,
+			let hasScannedForEncodings = plist[CodingKeys.hasScannedForEncodings]?.string,
+			let knownRegions = plist[CodingKeys.knownRegions]?.array,
+			let mainGroup = objectCache.object(for: PBXGlobalID(rawValue: plist[CodingKeys.mainGroup]?.string)) as? PBXGroup,
+			let productRefGroup = objectCache.object(for: PBXGlobalID(rawValue: plist[CodingKeys.productRefGroup]?.string)) as? PBXGroup,
+			let projectDirPath = plist[CodingKeys.projectDirPath]?.string,
+			let projectRoot = plist[CodingKeys.projectRoot]?.string,
+			let targets = plist[CodingKeys.targets]?.array
 			else {
 				fatalError()
 		}
@@ -172,12 +175,18 @@ public final class PBXProject: PBXObject, PBXContainer {
 		self.productRefGroup = productRefGroup
 		self.projectDirPath = projectDirPath
 		
-		if let projectReferences = plist["projectReferences"]?.objectArray() {
+		if let projectReferences = plist[CodingKeys.projectReferences]?.objectArray() {
 			self.projectReferences = Set(projectReferences.map {
 				XCProjectReferenceInfo(with: $0, objectCache: objectCache)
 			})
 		}
 		
+		if let packageReferences = plist[CodingKeys.packageReferences]?.array {
+			self.packageReferences = packageReferences.map { PBXGlobalID(rawValue: $0) }.compactMap {
+				objectCache.object(for: $0)
+			}
+		}
+		
 		self.projectRoot = projectRoot
 		self.targets = targets.compactMap {
 			let target: PBXTarget? = objectCache.object(for: PBXGlobalID(rawValue: $0))
@@ -221,6 +230,9 @@ public final class PBXProject: PBXObject, PBXContainer {
 			visitor.visit(object: $0.productGroup)
 			visitor.visit(object: $0.projectReference)
 		}
+		packageReferences?.forEach {
+			visitor.visit(object: $0)
+		}
 	}
 	
 	public override func encode(to encoder: Encoder) throws {
@@ -233,6 +245,7 @@ public final class PBXProject: PBXObject, PBXContainer {
 		try container.encode(hasScannedForEncodings, forKey: .hasScannedForEncodings)
 		try container.encode(knownRegions, forKey: .knownRegions)
 		try container.encode(mainGroup, forKey: .mainGroup)
+		try container.encodeIfPresent(packageReferences, forKey: .packageReferences)
 		try container.encode(productRefGroup, forKey: .productRefGroup)
 		try container.encodeIfPresent(projectDirPath, forKey: .projectDirPath)
 		try container.encodeIfPresent(projectReferences?.sorted(by: \XCProjectReferenceInfo.projectReference.displayName, using: String.caseInsensitiveCompare), forKey: .projectReferences)
diff --git a/Sources/XcodeProject/Objects/PBXTargetDependency.swift b/Sources/XcodeProject/Objects/PBXTargetDependency.swift
index 9a9e5dc..024ebd6 100644
--- a/Sources/XcodeProject/Objects/PBXTargetDependency.swift
+++ b/Sources/XcodeProject/Objects/PBXTargetDependency.swift
@@ -6,7 +6,9 @@
 //  Copyright © 2017 Geoffrey Foster. All rights reserved.
 //
 
-public class PBXTargetDependency: PBXObject {
+public class PBXTargetDependency: PBXProjectItem {
+	//addPackageProductDependency
+	//removePackageProductDependency
 	private enum CodingKeys: String, CodingKey {
 		case name
 		case target
@@ -39,9 +41,9 @@ public class PBXTargetDependency: PBXObject {
 	
 	override func update(with plist: PropertyList, objectCache: ObjectCache) {
 		super.update(with: plist, objectCache: objectCache)
-		self.name = plist["name"]?.string
-		self.target = objectCache.object(for: plist["target"]?.globalID)
-		self.targetProxy = objectCache.object(for: plist["targetProxy"]?.globalID)
+		self.name = plist[CodingKeys.name]?.string
+		self.target = objectCache.object(for: plist[CodingKeys.target]?.globalID)
+		self.targetProxy = objectCache.object(for: plist[CodingKeys.targetProxy]?.globalID)
 	}
 	
 	override func visit(_ visitor: ObjectVisitor) {
diff --git a/Sources/XcodeProject/Objects/References/PBXFileReference.swift b/Sources/XcodeProject/Objects/References/PBXFileReference.swift
index 03b8258..1ca65a5 100644
--- a/Sources/XcodeProject/Objects/References/PBXFileReference.swift
+++ b/Sources/XcodeProject/Objects/References/PBXFileReference.swift
@@ -24,9 +24,9 @@ public final class PBXFileReference: PBXReference {
 		case unknown
 		
 		static func from(_ plist: PropertyList) -> FileType {
-			if let lastKnownFileType = plist["lastKnownFileType"]?.string {
+			if let lastKnownFileType = plist[CodingKeys.lastKnownFileType]?.string {
 				return .lastKnown(lastKnownFileType)
-			} else if let explicitFileType = plist["explicitFileType"]?.string {
+			} else if let explicitFileType = plist[CodingKeys.explicitFileType]?.string {
 				return .explicit(explicitFileType)
 			} else {
 				return .unknown
@@ -73,14 +73,14 @@ public final class PBXFileReference: PBXReference {
 	override func update(with plist: PropertyList, objectCache: ObjectCache) {
 		super.update(with: plist, objectCache: objectCache)
 		
-		if let encoding = plist["fileEncoding"]?.uint {
+		if let encoding = plist[CodingKeys.fileEncoding]?.uint {
 			self.fileEncoding = String.Encoding(rawValue: encoding)
 		}
 		
-		self.includeInIndex = plist["includeInIndex"]?.bool
+		self.includeInIndex = plist[CodingKeys.includeInIndex]?.bool
 		self.fileType = FileType.from(plist)
-		self.xcLanguageSpecificationIdentifier = plist["xcLanguageSpecificationIdentifier"]?.string
-		self.wrapsLines = plist["wrapsLines"]?.bool
+		self.xcLanguageSpecificationIdentifier = plist[CodingKeys.xcLanguageSpecificationIdentifier]?.string
+		self.wrapsLines = plist[CodingKeys.wrapsLines]?.bool
 	}
 	
 	public override func encode(to encoder: Encoder) throws {
diff --git a/Sources/XcodeProject/Objects/References/PBXGroup.swift b/Sources/XcodeProject/Objects/References/PBXGroup.swift
index 4f8e6fc..0297e7b 100644
--- a/Sources/XcodeProject/Objects/References/PBXGroup.swift
+++ b/Sources/XcodeProject/Objects/References/PBXGroup.swift
@@ -44,7 +44,7 @@ public class PBXGroup: PBXReference {
 	
 	override func update(with plist: PropertyList, objectCache: ObjectCache) {
 		super.update(with: plist, objectCache: objectCache)
-		self.children = plist["children"]?.array?.map { return PBXGlobalID(rawValue: $0) }.compactMap { objectCache.object(for: $0) as? PBXReference } ?? []
+		self.children = plist[CodingKeys.children]?.array?.map { return PBXGlobalID(rawValue: $0) }.compactMap { objectCache.object(for: $0) as? PBXReference } ?? []
 	}
 	
 	override func visit(_ visitor: ObjectVisitor) {
diff --git a/Sources/XcodeProject/Objects/References/PBXReference.swift b/Sources/XcodeProject/Objects/References/PBXReference.swift
index 1e734b2..d4fdf4d 100644
--- a/Sources/XcodeProject/Objects/References/PBXReference.swift
+++ b/Sources/XcodeProject/Objects/References/PBXReference.swift
@@ -8,7 +8,7 @@
 
 import Foundation
 
-public class PBXReference: PBXObject {
+public class PBXReference: PBXContainerItem {
 	private enum CodingKeys: String, CodingKey {
 		case name
 		case path
@@ -26,6 +26,7 @@ public class PBXReference: PBXObject {
 		case builtProducts = "BUILT_PRODUCTS_DIR"
 		case developerDir = "DEVELOPER_DIR"
 		case sdkRoot = "SDKROOT"
+		case unknown = "<unknown>"
 	}
 	
 	public enum LineEnding: Int8, Encodable {
@@ -102,15 +103,15 @@ public class PBXReference: PBXObject {
 	// MARK: - PList Unarchiving
 	override func update(with plist: PropertyList, objectCache: ObjectCache) {
 		super.update(with: plist, objectCache: objectCache)
-		self.path = plist["path"]?.string
-		self.name = plist["name"]?.string
-		self.sourceTree = SourceTree(rawValue: plist["sourceTree"]?.string ?? "")
-		self.usesTabs = plist["usesTabs"]?.bool
-		self.tabWidth = plist["tabWidth"]?.int
-		if let lineEnding = plist["lineEnding"]?.int8 {
+		self.path = plist[CodingKeys.path]?.string
+		self.name = plist[CodingKeys.name]?.string
+		self.sourceTree = SourceTree(rawValue: plist[CodingKeys.sourceTree]?.string ?? "")
+		self.usesTabs = plist[CodingKeys.usesTabs]?.bool
+		self.tabWidth = plist[CodingKeys.tabWidth]?.int
+		if let lineEnding = plist[CodingKeys.lineEnding]?.int8 {
 			self.lineEnding = LineEnding(rawValue: lineEnding)
 		}
-		self.indentWidth = plist["indentWidth"]?.int
+		self.indentWidth = plist[CodingKeys.indentWidth]?.int
 	}
 	
 	override var archiveComment: String {
diff --git a/Sources/XcodeProject/Objects/References/PBXReferenceProxy.swift b/Sources/XcodeProject/Objects/References/PBXReferenceProxy.swift
index 23f5d7e..1428b80 100644
--- a/Sources/XcodeProject/Objects/References/PBXReferenceProxy.swift
+++ b/Sources/XcodeProject/Objects/References/PBXReferenceProxy.swift
@@ -31,8 +31,8 @@ public final class PBXReferenceProxy: PBXReference {
 	
 	override func update(with plist: PropertyList, objectCache: ObjectCache) {
 		super.update(with: plist, objectCache: objectCache)
-		self.fileType = plist["fileType"]?.string
-		self.remoteRef = objectCache.object(for: PBXGlobalID(rawValue: plist["remoteRef"]?.string)) as? PBXContainerItemProxy
+		self.fileType = plist[CodingKeys.fileType]?.string
+		self.remoteRef = objectCache.object(for: PBXGlobalID(rawValue: plist[CodingKeys.remoteRef]?.string)) as? PBXContainerItemProxy
 		self.sourceTree = sourceTree
 	}
 	
diff --git a/Sources/XcodeProject/Objects/References/XCVersionGroup.swift b/Sources/XcodeProject/Objects/References/XCVersionGroup.swift
index 6126d32..1f7ece8 100644
--- a/Sources/XcodeProject/Objects/References/XCVersionGroup.swift
+++ b/Sources/XcodeProject/Objects/References/XCVersionGroup.swift
@@ -33,8 +33,8 @@ public final class XCVersionGroup: PBXGroup {
 		super.update(with: plist, objectCache: objectCache)
 		
 		guard
-			let currentVersion = objectCache.object(for: PBXGlobalID(rawValue: plist["currentVersion"]?.string)) as? PBXFileReference,
-			let versionGroupType = plist["versionGroupType"]?.string
+			let currentVersion = objectCache.object(for: PBXGlobalID(rawValue: plist[CodingKeys.currentVersion]?.string)) as? PBXFileReference,
+			let versionGroupType = plist[CodingKeys.versionGroupType]?.string
 			else {
 				fatalError()
 		}
diff --git a/Sources/XcodeProject/Objects/Swift Package/XCLocalSwiftPackageReference.swift b/Sources/XcodeProject/Objects/Swift Package/XCLocalSwiftPackageReference.swift
new file mode 100644
index 0000000..9ea965e
--- /dev/null
+++ b/Sources/XcodeProject/Objects/Swift Package/XCLocalSwiftPackageReference.swift	
@@ -0,0 +1,17 @@
+//
+//  XCLocalSwiftPackageReference.swift
+//  
+//
+//  Created by Geoffrey Foster on 2019-07-03.
+//
+
+import Foundation
+
+final class XCLocalSwiftPackageReference: XCSwiftPackageReference {
+	var packageName: String?
+	
+	override var archiveComment: String {
+		guard let packageName = packageName else { return super.archiveComment }
+		return #"\#(super.archiveComment) "\#(packageName)""#
+	}
+}
diff --git a/Sources/XcodeProject/Objects/Swift Package/XCRemoteSwiftPackageReference.swift b/Sources/XcodeProject/Objects/Swift Package/XCRemoteSwiftPackageReference.swift
new file mode 100644
index 0000000..856f12a
--- /dev/null
+++ b/Sources/XcodeProject/Objects/Swift Package/XCRemoteSwiftPackageReference.swift	
@@ -0,0 +1,156 @@
+//
+//  XCRemoteSwiftPackageReference.swift
+//  
+//
+//  Created by Geoffrey Foster on 2019-07-03.
+//
+
+import Foundation
+
+public final class XCRemoteSwiftPackageReference: XCSwiftPackageReference {
+	public enum Requirement: Encodable {
+		private enum CodingKeys: String, CodingKey {
+			case kind
+			case minimumVersion
+			case maximumVersion
+			case version
+			case branch
+			case revision
+		}
+
+		public struct Version: CustomStringConvertible, Encodable {
+			let major: Int
+			let minor: Int
+			let patch: Int
+
+			public init(major: Int, minor: Int, patch: Int) {
+				self.major = major
+				self.minor = minor
+				self.patch = patch
+			}
+			
+			init?(_ value: String) {
+				var integerValues = value.components(separatedBy: ".").compactMap { Int($0) }
+				guard integerValues.count == 3 else { return nil }
+				self.init(major: integerValues.removeFirst(), minor: integerValues.removeFirst(), patch: integerValues.removeFirst())
+			}
+			
+			public var description: String {
+				return "\(major).\(minor).\(patch)"
+			}
+			
+			public func encode(to encoder: Encoder) throws {
+				var container = encoder.singleValueContainer()
+				try container.encode(description)
+			}
+		}
+		
+		public struct GitHash: Encodable, CustomStringConvertible {
+			private var value: String
+			init?(_ value: String) {
+				// TODO: verify [0-9a-zA-Z] and exactly 40 characters, SHA-1 hash
+				//value.trimmingCharacters(in: CharacterSet.)
+				self.value = value
+			}
+			
+			public var description: String {
+				return value
+			}
+			
+			public func encode(to encoder: Encoder) throws {
+				var container = encoder.singleValueContainer()
+				try container.encode(description)
+			}
+		}
+		case upToNextMinorVersion(Version)
+		case upToNextMajorVersion(Version)
+		case versionRange(from: Version, to: Version)
+		case exactVersion(Version)
+		case branch(String)
+		case revision(GitHash)
+		
+		init?(plist: PropertyList) {
+			guard let kind = plist[CodingKeys.kind]?.string else { return nil }
+			switch kind {
+			case "upToNextMinorVersion":
+				guard let versionString = plist[CodingKeys.minimumVersion]?.string, let version = Version(versionString) else { return nil }
+				self = .upToNextMinorVersion(version)
+			case "upToNextMajorVersion":
+				guard let versionString = plist[CodingKeys.minimumVersion]?.string, let version = Version(versionString) else { return nil }
+				self = .upToNextMajorVersion(version)
+			case "versionRange":
+				guard let minimumVersionString = plist[CodingKeys.minimumVersion]?.string,
+					let minimumVersion = Version(minimumVersionString),
+					let maximumVersionString = plist[CodingKeys.maximumVersion]?.string,
+					let maximumVersion = Version(maximumVersionString) else {
+						return nil
+				}
+				self = .versionRange(from: minimumVersion, to: maximumVersion)
+			case "exactVersion":
+				guard let versionString = plist[CodingKeys.version]?.string, let version = Version(versionString) else { return nil }
+				self = .exactVersion(version)
+			case "branch":
+				guard let branch = plist[CodingKeys.branch]?.string else { return nil }
+				self = .branch(branch)
+			case "revision":
+				guard let revisionString = plist[CodingKeys.revision]?.string, let revision = GitHash(revisionString) else { return nil }
+				self = .revision(revision)
+			default:
+				return nil
+			}
+		}
+		
+		public func encode(to encoder: Encoder) throws {
+			var container = encoder.container(keyedBy: CodingKeys.self)
+			switch self {
+			case .upToNextMinorVersion(let version):
+				try container.encode("upToNextMinorVersion", forKey: .kind)
+				try container.encode(version, forKey: .minimumVersion)
+			case .upToNextMajorVersion(let version):
+				try container.encode("upToNextMajorVersion", forKey: .kind)
+				try container.encode(version, forKey: .minimumVersion)
+			case .versionRange(let from, let to):
+				try container.encode("versionRange", forKey: .kind)
+				try container.encode(from, forKey: .minimumVersion)
+				try container.encode(to, forKey: .maximumVersion)
+			case .exactVersion(let version):
+				try container.encode("exactVersion", forKey: .kind)
+				try container.encode(version, forKey: .version)
+			case .branch(let branch):
+				try container.encode("branch", forKey: .kind)
+				try container.encode(branch, forKey: .branch)
+			case .revision(let revision):
+				try container.encode("revision", forKey: .kind)
+				try container.encode(revision, forKey: .revision)
+			}
+		}
+	}
+	
+	private enum CodingKeys: String, CodingKey {
+		case repositoryURL
+		case requirement
+	}
+
+	var repositoryURL: String?
+	var requirement: Requirement?
+	
+	override var archiveComment: String {
+		guard let repositoryURL = repositoryURL, let url = URL(string: repositoryURL) else { return super.archiveComment }
+		return #"\#(super.archiveComment) "\#(url.deletingPathExtension().lastPathComponent)""#
+	}
+	
+	override func update(with plist: PropertyList, objectCache: ObjectCache) {
+		super.update(with: plist, objectCache: objectCache)
+		self.repositoryURL = plist[CodingKeys.repositoryURL]?.string
+		if let requirementPlist = plist[CodingKeys.requirement] {
+			self.requirement = Requirement(plist: requirementPlist)
+		}
+	}
+	
+	public override func encode(to encoder: Encoder) throws {
+		try super.encode(to: encoder)
+		var container = encoder.container(keyedBy: CodingKeys.self)
+		try container.encodeIfPresent(repositoryURL, forKey: .repositoryURL)
+		try container.encodeIfPresent(requirement, forKey: .requirement)
+	}
+}
diff --git a/Sources/XcodeProject/Objects/Swift Package/XCSwiftPackageProductDependency.swift b/Sources/XcodeProject/Objects/Swift Package/XCSwiftPackageProductDependency.swift
new file mode 100644
index 0000000..a70f02b
--- /dev/null
+++ b/Sources/XcodeProject/Objects/Swift Package/XCSwiftPackageProductDependency.swift	
@@ -0,0 +1,35 @@
+//
+//  XCSwiftPackageProductDependency.swift
+//  
+//
+//  Created by Geoffrey Foster on 2019-07-03.
+//
+
+import Foundation
+
+public final class XCSwiftPackageProductDependency: PBXProductDependency {
+	private enum CodingKeys: String, CodingKey {
+		case packageReference = "package"
+		case productName
+	}
+	
+	var packageReference: XCSwiftPackageReference?
+	var productName: String?
+	
+	override var archiveComment: String {
+		return productName ?? super.archiveComment
+	}
+	
+	override func update(with plist: PropertyList, objectCache: ObjectCache) {
+		super.update(with: plist, objectCache: objectCache)
+		self.productName = plist[CodingKeys.productName]?.string
+		self.packageReference = objectCache.object(for: PBXGlobalID(rawValue: plist[CodingKeys.packageReference]?.string))
+	}
+	
+	public override func encode(to encoder: Encoder) throws {
+		try super.encode(to: encoder)
+		var container = encoder.container(keyedBy: CodingKeys.self)
+		try container.encodeIfPresent(packageReference, forKey: .packageReference)
+		try container.encodeIfPresent(productName, forKey: .productName)
+	}
+}
diff --git a/Sources/XcodeProject/Objects/Swift Package/XCSwiftPackageReference.swift b/Sources/XcodeProject/Objects/Swift Package/XCSwiftPackageReference.swift
new file mode 100644
index 0000000..755bff3
--- /dev/null
+++ b/Sources/XcodeProject/Objects/Swift Package/XCSwiftPackageReference.swift	
@@ -0,0 +1,12 @@
+//
+//  XCSwiftPackageReference.swift
+//  
+//
+//  Created by Geoffrey Foster on 2019-07-03.
+//
+
+import Foundation
+
+public class XCSwiftPackageReference: PBXProjectItem {
+	
+}
diff --git a/Sources/XcodeProject/Objects/Targets/PBXLegacyTarget.swift b/Sources/XcodeProject/Objects/Targets/PBXLegacyTarget.swift
index 955bd65..3f67cc5 100644
--- a/Sources/XcodeProject/Objects/Targets/PBXLegacyTarget.swift
+++ b/Sources/XcodeProject/Objects/Targets/PBXLegacyTarget.swift
@@ -22,10 +22,10 @@ public final class PBXLegacyTarget: PBXTarget {
 	override func update(with plist: PropertyList, objectCache: ObjectCache) {
 		super.update(with: plist, objectCache: objectCache)
 		
-		self.buildArguments = plist["buildArgumentsString"]?.string
-		self.buildToolPath = plist["buildToolPath"]?.string
-		self.buildWorkingDirectory = plist["buildWorkingDirectory"]?.string
-		if let passBuildSettingsInEnvironment = plist["passBuildSettingsInEnvironment"]?.bool {
+		self.buildArguments = plist[CodingKeys.buildArgumentsString]?.string
+		self.buildToolPath = plist[CodingKeys.buildToolPath]?.string
+		self.buildWorkingDirectory = plist[CodingKeys.buildWorkingDirectory]?.string
+		if let passBuildSettingsInEnvironment = plist[CodingKeys.passBuildSettingsInEnvironment]?.bool {
 			self.passBuildSettingsInEnvironment = passBuildSettingsInEnvironment
 		}
 	}
diff --git a/Sources/XcodeProject/Objects/Targets/PBXNativeTarget.swift b/Sources/XcodeProject/Objects/Targets/PBXNativeTarget.swift
index 06a6a51..c778124 100644
--- a/Sources/XcodeProject/Objects/Targets/PBXNativeTarget.swift
+++ b/Sources/XcodeProject/Objects/Targets/PBXNativeTarget.swift
@@ -39,7 +39,7 @@ public final class PBXNativeTarget: PBXTarget {
 		super.update(with: plist, objectCache: objectCache)
 		
 		guard
-			let productType = ProductType(rawValue: plist["productType"]?.string ?? "")
+			let productType = ProductType(rawValue: plist[CodingKeys.productType]?.string ?? "")
 			else {
 				fatalError()
 		}
diff --git a/Sources/XcodeProject/Objects/Targets/PBXTarget.swift b/Sources/XcodeProject/Objects/Targets/PBXTarget.swift
index 6da370f..5e0f10e 100644
--- a/Sources/XcodeProject/Objects/Targets/PBXTarget.swift
+++ b/Sources/XcodeProject/Objects/Targets/PBXTarget.swift
@@ -6,13 +6,14 @@
 //  Copyright © 2017 Geoffrey Foster. All rights reserved.
 //
 
-public class PBXTarget: PBXObject, PBXContainer {
+public class PBXTarget: PBXProjectItem, PBXContainer {
 	private enum CodingKeys: String, CodingKey {
 		case buildConfigurationList
 		case buildPhases
 		case buildRules
 		case dependencies
 		case name
+		case packageProductDependencies
 		case productName
 		case productReference
 	}
@@ -53,6 +54,7 @@ public class PBXTarget: PBXObject, PBXContainer {
 			productReference?.parent = self
 		}
 	}
+	var packageProductDependencies: [XCSwiftPackageProductDependency]?
 	
 	override func willMove(from: PBXObject?) {
 		super.willMove(from: from)
@@ -76,28 +78,34 @@ public class PBXTarget: PBXObject, PBXContainer {
 		super.update(with: plist, objectCache: objectCache)
 		
 		guard
-			let buildConfigurationListID = PBXGlobalID(rawValue: plist["buildConfigurationList"]?.string),
+			let buildConfigurationListID = PBXGlobalID(rawValue: plist[CodingKeys.buildConfigurationList]?.string),
 			let buildConfigurationList = objectCache.object(for: buildConfigurationListID) as? XCConfigurationList,
-			let buildPhases = plist["buildPhases"]?.array,
-			let dependencies = plist["dependencies"]?.array,
-			let name = plist["name"]?.string,
-			let productName = plist["productName"]?.string
+			let buildPhases = plist[CodingKeys.buildPhases]?.array,
+			let dependencies = plist[CodingKeys.dependencies]?.array,
+			let name = plist[CodingKeys.name]?.string,
+			let productName = plist[CodingKeys.productName]?.string
 			else {
 				fatalError()
 		}
 		self.name = name
 		self.productName = productName
-		self.productReference = objectCache.object(for: PBXGlobalID(rawValue: plist["productReference"]?.string)) as? PBXFileReference
+		self.productReference = objectCache.object(for: PBXGlobalID(rawValue: plist[CodingKeys.productReference]?.string)) as? PBXFileReference
 		self.buildConfigurationList = buildConfigurationList
 		self.buildPhases = buildPhases.compactMap {
 			return objectCache.object(for: PBXGlobalID(rawValue: $0)) as? PBXBuildPhase
 		}
-		self.buildRules = plist["buildRules"]?.array?.compactMap {
+		self.buildRules = plist[CodingKeys.buildRules]?.array?.compactMap {
 			return objectCache.object(for: PBXGlobalID(rawValue: $0)) as? PBXBuildRule
 		}
 		self.dependencies = dependencies.compactMap {
 			return objectCache.object(for: PBXGlobalID(rawValue: $0)) as? PBXTargetDependency
 		}
+		
+		if let packageProductDependencies = plist[CodingKeys.packageProductDependencies]?.array {
+			self.packageProductDependencies = packageProductDependencies.map { PBXGlobalID(rawValue: $0) }.compactMap {
+				objectCache.object(for: $0)
+			}
+		}
 	}
 	
 	override var archiveComment: String {
@@ -113,6 +121,9 @@ public class PBXTarget: PBXObject, PBXContainer {
 		dependencies.forEach {
 			visitor.visit(object: $0)
 		}
+		packageProductDependencies?.forEach {
+			visitor.visit(object: $0)
+		}
 		visitor.visit(object: productReference)
 	}
 	
@@ -124,6 +135,9 @@ public class PBXTarget: PBXObject, PBXContainer {
 		try container.encodeIfPresent(buildRules, forKey: .buildRules)
 		try container.encode(dependencies, forKey: .dependencies)
 		try container.encodeIfPresent(name, forKey: .name)
+		if encoder.objectVersion >= .xcode11 {
+			try container.encodeIfPresent(packageProductDependencies, forKey: .packageProductDependencies)
+		}
 		try container.encodeIfPresent(productName, forKey: .productName)
 		try container.encodeIfPresent(productReference, forKey: .productReference)
 	}
diff --git a/Sources/XcodeProject/Objects/XCBuildConfiguration.swift b/Sources/XcodeProject/Objects/XCBuildConfiguration.swift
index 3ca94a2..5e6474e 100644
--- a/Sources/XcodeProject/Objects/XCBuildConfiguration.swift
+++ b/Sources/XcodeProject/Objects/XCBuildConfiguration.swift
@@ -29,15 +29,15 @@ final class XCBuildConfiguration: PBXObject {
 		super.update(with: plist, objectCache: objectCache)
 		
 		guard
-			let name = plist["name"]?.string,
-			let buildSettings = plist["buildSettings"]?.dictionary
+			let name = plist[CodingKeys.name]?.string,
+			let buildSettings = plist[CodingKeys.buildSettings]?.dictionary
 			else {
 				fatalError()
 		}
 		
 		self.name = name
 		self.buildSettings = BuildSettings(buildSettings)
-		self.baseConfigurationReference = objectCache.object(for: plist["baseConfigurationReference"]?.globalID)
+		self.baseConfigurationReference = objectCache.object(for: plist[CodingKeys.baseConfigurationReference]?.globalID)
 	}
 	
 	override var archiveComment: String {
diff --git a/Sources/XcodeProject/Objects/XCConfigurationList.swift b/Sources/XcodeProject/Objects/XCConfigurationList.swift
index 8da89cf..571b367 100644
--- a/Sources/XcodeProject/Objects/XCConfigurationList.swift
+++ b/Sources/XcodeProject/Objects/XCConfigurationList.swift
@@ -6,7 +6,7 @@
 //  Copyright © 2017 Geoffrey Foster. All rights reserved.
 //
 
-final class XCConfigurationList: PBXObject {
+final class XCConfigurationList: PBXProjectItem {
 	private enum CodingKeys: String, CodingKey {
 		case buildConfigurations
 		case defaultConfigurationIsVisible
@@ -45,15 +45,15 @@ final class XCConfigurationList: PBXObject {
 		super.update(with: plist, objectCache: objectCache)
 		
 		guard
-			let buildConfigurations = PBXGlobalID.ids(from: plist["buildConfigurations"]?.array),
-			let defaultConfigurationIsVisibleString = plist["defaultConfigurationIsVisible"]?.string
+			let buildConfigurations = PBXGlobalID.ids(from: plist[CodingKeys.buildConfigurations]?.array),
+			let defaultConfigurationIsVisibleString = plist[CodingKeys.defaultConfigurationIsVisible]?.string
 			else {
 				fatalError()
 		}
 		
 		self.buildConfigurations = buildConfigurations.compactMap { objectCache.object(for: $0) }
 		self.defaultConfigurationIsVisible = Int(defaultConfigurationIsVisibleString) != 0
-		self.defaultConfigurationName = plist["defaultConfigurationName"]?.string
+		self.defaultConfigurationName = plist[CodingKeys.defaultConfigurationName]?.string
 	}
 	
 	override public func visit(_ visitor: ObjectVisitor) {
diff --git a/Sources/XcodeProject/Objects/XCProjectReferenceInfo.swift b/Sources/XcodeProject/Objects/XCProjectReferenceInfo.swift
index 9652f1b..5b18641 100644
--- a/Sources/XcodeProject/Objects/XCProjectReferenceInfo.swift
+++ b/Sources/XcodeProject/Objects/XCProjectReferenceInfo.swift
@@ -7,7 +7,7 @@
 
 import Foundation
 
-final class XCProjectReferenceInfo: Hashable, Encodable {
+final class XCProjectReferenceInfo: Hashable, Encodable { // PBXProjectItem
 	static func == (lhs: XCProjectReferenceInfo, rhs: XCProjectReferenceInfo) -> Bool {
 		return lhs.productGroup == rhs.productGroup && lhs.projectReference == rhs.projectReference
 	}
diff --git a/Sources/XcodeProject/ProjectFile.swift b/Sources/XcodeProject/ProjectFile.swift
index cc60f2d..9c7d09a 100644
--- a/Sources/XcodeProject/ProjectFile.swift
+++ b/Sources/XcodeProject/ProjectFile.swift
@@ -19,6 +19,7 @@ public enum ObjectVersion: UInt, Comparable, CaseIterable {
 	case xcode8 = 48
 	case xcode93 = 50
 	case xcode10 = 51
+	case xcode11 = 52
 }
 
 public final class ProjectFile {
diff --git a/Tests/XcodeProjectTests/XcodeProjectTests.swift b/Tests/XcodeProjectTests/XcodeProjectTests.swift
index fa12f96..410cc51 100644
--- a/Tests/XcodeProjectTests/XcodeProjectTests.swift
+++ b/Tests/XcodeProjectTests/XcodeProjectTests.swift
@@ -41,7 +41,7 @@ class XcodeProjectTests: XCTestCase {
 			try streamWriter.string.write(to: failureURL, atomically: true, encoding: .utf8)
 			add(XCTAttachment(contentsOfFile: failureURL))
 			
-			XCTFail("Failed to generate matching output for \(url.lastPathComponent). Run ksdiff \(url.path) \(failureURL.path)")
+			XCTFail(#"Failed to generate matching output for \#(url.lastPathComponent). Run ksdiff "\#(url.path)" "\#(failureURL.path)""#)
 		}
 	}