diff --git a/JsonFlatFileDataStore.Test/CollectionQueryTests.cs b/JsonFlatFileDataStore.Test/CollectionQueryTests.cs
index 24dffdd..3606060 100644
--- a/JsonFlatFileDataStore.Test/CollectionQueryTests.cs
+++ b/JsonFlatFileDataStore.Test/CollectionQueryTests.cs
@@ -1,4 +1,5 @@
-using System.Linq;
+using System;
+using System.Linq;
 using Newtonsoft.Json.Linq;
 using Xunit;
 
@@ -81,6 +82,31 @@ public void GetNextIdValue_StringType()
             Assert.Equal("SomeValue1", nextId);
         }
 
+        [Fact]
+        public void GetNextIdValue_GuidType()
+        {
+            var newFilePath = UTHelpers.Up();
+
+            var store = new DataStore(newFilePath, keyProperty: "helloField");
+
+            var collection = store.GetCollection("collectionWithGuidId");
+
+            var shouldBeNone = collection.GetNextIdValue();
+            Assert.Equal(0, shouldBeNone);
+
+            collection.InsertOne(new { helloField = Guid.NewGuid() });
+
+            var inserted = collection.AsQueryable().First();
+
+            var nextId = collection.GetNextIdValue();
+            Assert.IsType<Guid>(nextId);
+
+            collection.InsertOne(new { helloField = nextId });
+
+            nextId = collection.GetNextIdValue();
+            Assert.IsType<Guid>(nextId);
+        }
+
         [Fact]
         public void GetNextIdValue_StringType_AnonymousType()
         {
diff --git a/JsonFlatFileDataStore.Test/DataStoreTests.cs b/JsonFlatFileDataStore.Test/DataStoreTests.cs
index f994b03..d741f80 100644
--- a/JsonFlatFileDataStore.Test/DataStoreTests.cs
+++ b/JsonFlatFileDataStore.Test/DataStoreTests.cs
@@ -556,7 +556,7 @@ public void FileNotFound_CreateNewFile_Encrypted()
 
             UTHelpers.Down(path);
         }
-        
+
         [Fact]
         public void File_Has_Correct_PropertyNames_DynamicCollection()
         {
@@ -604,7 +604,7 @@ public void File_Has_Correct_PropertyNames_TypedCollection()
             var assertCollection = store.GetCollection<Employee>();
             Assert.Equal(3, assertCollection.Count);
         }
-        
+
         [Fact]
         public void File_Has_Correct_PropertyNames_Single_Item()
         {
@@ -621,6 +621,34 @@ public void File_Has_Correct_PropertyNames_Single_Item()
             Assert.Equal(1, propCount);
         }
 
+        [Fact]
+        public void Model_With_Guids()
+        {
+            var pathToJson = UTHelpers.Up();
+
+            var store = new DataStore(pathToJson);
+
+            var typedCollection = store.GetCollection<TestModelWithGuid>();
+
+            var itemId = Guid.NewGuid();
+            var secondGuid = Guid.NewGuid();
+            var thirdGuid = Guid.NewGuid();
+
+            typedCollection.InsertOne(new TestModelWithGuid { Id = itemId, Name = "Jim", OtherGuid = secondGuid });
+            typedCollection.ReplaceOne(e => e.Id == itemId, new TestModelWithGuid { Id = itemId, Name = "Barry", OtherGuid = secondGuid });
+            typedCollection.UpdateOne(e => e.Id == itemId, new { Name = "Sandels" });
+            typedCollection.UpdateOne(e => e.Id == itemId, new { OtherGuid = thirdGuid });
+
+            var userTyped = typedCollection
+                            .AsQueryable()
+                            .Single(p => p.Name == "Sandels");
+
+            Assert.Equal("Sandels", userTyped.Name);
+            Assert.Equal(thirdGuid, userTyped.OtherGuid);
+
+            UTHelpers.Down(pathToJson);
+        }
+
         public class Employee
         {
             public int Id { get; set; }
diff --git a/JsonFlatFileDataStore.Test/TestModels.cs b/JsonFlatFileDataStore.Test/TestModels.cs
index 33618b6..e6b2459 100644
--- a/JsonFlatFileDataStore.Test/TestModels.cs
+++ b/JsonFlatFileDataStore.Test/TestModels.cs
@@ -163,4 +163,14 @@ public class World
 
         public float CameraRotationY { get; set; }
     }
+
+    public class TestModelWithGuid
+    {
+        public Guid Id { get; set; }
+
+        public string Name { get; set; }
+
+        public Guid OtherGuid { get; set; }
+
+    }
 }
\ No newline at end of file
diff --git a/JsonFlatFileDataStore/DocumentCollection.cs b/JsonFlatFileDataStore/DocumentCollection.cs
index 469cdc9..bac9ff0 100644
--- a/JsonFlatFileDataStore/DocumentCollection.cs
+++ b/JsonFlatFileDataStore/DocumentCollection.cs
@@ -394,6 +394,9 @@ private bool ExecuteLocked(Func<List<T>, bool> func, List<T> data)
                         if (primaryKeyValue is Int64)
                             return (int)primaryKeyValue;
 
+                        if (Guid.TryParse(primaryKeyValue, out Guid guidValue))
+                            return guidValue;
+
                         return primaryKeyValue;
                     }
                 }
@@ -411,6 +414,9 @@ private bool ExecuteLocked(Func<List<T>, bool> func, List<T> data)
             if (keyValue is Int64)
                 return (int)keyValue + 1;
 
+            if (keyValue is Guid)
+                return Guid.NewGuid();
+
             return ParseNextIntegerToKeyValue(keyValue.ToString());
         }