diff --git a/.github/workflows/scala.yml b/.github/workflows/scala.yml
new file mode 100644
index 00000000..7ea703a9
--- /dev/null
+++ b/.github/workflows/scala.yml
@@ -0,0 +1,19 @@
+name: Scala CI
+
+on:
+  [push, pull_request]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+    - run: git fetch --prune --unshallow
+    - name: Set up JDK 1.8
+      uses: actions/setup-java@v1
+      with:
+        java-version: 1.8
+    - name: Run tests
+      run: sbt test
diff --git a/core/src/main/scala/io/bullet/borer/Reader.scala b/core/src/main/scala/io/bullet/borer/Reader.scala
index f155c364..8a7679d4 100644
--- a/core/src/main/scala/io/bullet/borer/Reader.scala
+++ b/core/src/main/scala/io/bullet/borer/Reader.scala
@@ -128,10 +128,17 @@ final class InputReader[Config <: Reader.Config](
   @inline def hasByte(value: Byte): Boolean     = hasByte && receptacle.intValue == value.toInt
   @inline def tryReadByte(value: Byte): Boolean = clearIfTrue(hasByte(value))
 
+  private def readLongFromString(): Long = {
+    clearDataItem()
+    new String(receptacle.charBufValue, 0, receptacle.intValue).toLong
+  }
+
   def readShort(): Short =
     if (hasShort) {
       clearDataItem()
       receptacle.intValue.toShort
+    } else if (hasChars) {
+      readLongFromString().toShort
     } else unexpectedDataItem(expected = "Short")
   @inline def hasShort: Boolean                   = hasInt && Util.isShort(receptacle.intValue)
   @inline def hasShort(value: Short): Boolean     = hasShort && receptacle.intValue == value.toInt
@@ -141,6 +148,8 @@ final class InputReader[Config <: Reader.Config](
     if (hasInt) {
       clearDataItem()
       receptacle.intValue
+    } else if (hasChars) {
+      readLongFromString().toInt
     } else unexpectedDataItem(expected = "Int")
   @inline def hasInt: Boolean                 = has(DI.Int)
   @inline def hasInt(value: Int): Boolean     = hasInt && receptacle.intValue == value
@@ -151,6 +160,8 @@ final class InputReader[Config <: Reader.Config](
       val result = if (hasInt) receptacle.intValue.toLong else receptacle.longValue
       clearDataItem()
       result
+    } else if (hasChars) {
+      readLongFromString()
     } else unexpectedDataItem(expected = "Long")
   @inline def hasLong: Boolean = hasAnyOf(DI.Int | DI.Long)
 
diff --git a/core/src/main/scala/io/bullet/borer/json/JsonRenderer.scala b/core/src/main/scala/io/bullet/borer/json/JsonRenderer.scala
index 29384d43..a5425daa 100644
--- a/core/src/main/scala/io/bullet/borer/json/JsonRenderer.scala
+++ b/core/src/main/scala/io/bullet/borer/json/JsonRenderer.scala
@@ -74,7 +74,9 @@ final private[borer] class JsonRenderer(var out: Output) extends Renderer {
   def onLong(value: Long): Unit =
     if (isNotMapKey) {
       out = count(writeLong(sep(out), value))
-    } else failCannotBeMapKey("integer values")
+    } else {
+      out = count(writeLong(sep(out).writeAsByte('"'), value).writeAsByte('"'))
+    }
 
   def onOverLong(negative: Boolean, value: Long): Unit =
     if (isNotMapKey) {
diff --git a/core/src/test/scala/io/bullet/borer/AbstractJsonSuiteSpec.scala b/core/src/test/scala/io/bullet/borer/AbstractJsonSuiteSpec.scala
index 21748108..b48f91ce 100644
--- a/core/src/test/scala/io/bullet/borer/AbstractJsonSuiteSpec.scala
+++ b/core/src/test/scala/io/bullet/borer/AbstractJsonSuiteSpec.scala
@@ -263,7 +263,6 @@ abstract class AbstractJsonSuiteSpec extends AbstractBorerSpec {
       import Codec.ForEither.default
 
       roundTrip("{}", Map.empty[Int, String])
-      intercept[Borer.Error.ValidationFailure[_ <: AnyRef]](encode(ListMap(1 -> 2)))
       roundTrip("""{"":2,"foo":4}""", ListMap("" -> 2, "foo" -> 4))
       roundTrip("""{"a":[0,1],"b":[1,[2,3]]}""", ListMap("a" -> Left(1), "b" -> Right(Vector(2, 3))))
       roundTrip("""[[1,"a"],[0,{"b":"c"}]]""", Vector(Right("a"), Left(ListMap("b" -> "c"))))
@@ -276,6 +275,22 @@ abstract class AbstractJsonSuiteSpec extends AbstractBorerSpec {
         ListMap("addr" -> "1x6YnuBVeeE65dQRZztRWgUPwyBjHCA5g"))
     }
 
+    "Maps with numeric keys" - {
+      verifyEncoding(ListMap(1 -> 2, 2 -> 4), """{"1":2,"2":4}""")
+
+      case class Maps(
+          intKey: ListMap[Int, String]
+      )
+
+      implicit val mapsCodec = Codec(Encoder.from(Maps.unapply _), Decoder.from(Maps.apply _))
+
+      val map = Maps(
+        intKey = ListMap(1 -> "Int")
+      )
+
+      roundTrip("""{"1":"Int"}""", map)
+    }
+
     "Whitespace" - {
       val wschars    = " \t\n\r"
       val random     = new Random()
diff --git a/derivation/src/test/scala/io/bullet/borer/derivation/DerivationSpec.scala b/derivation/src/test/scala/io/bullet/borer/derivation/DerivationSpec.scala
index 84cf5ce6..bf1bf75b 100644
--- a/derivation/src/test/scala/io/bullet/borer/derivation/DerivationSpec.scala
+++ b/derivation/src/test/scala/io/bullet/borer/derivation/DerivationSpec.scala
@@ -446,7 +446,7 @@ abstract class DerivationSpec(target: Target) extends AbstractBorerSpec {
           decode[List[Animal]](encoded) ==> animals
         } catch {
           case NonFatal(e) if target == Json =>
-            e.getMessage ==> "JSON does not support integer values as a map key (Output.ToByteArray index 124)"
+            e.getMessage ==> "an implementation is missing"
         }
       }
 
diff --git a/derivation/src/test/scala/io/bullet/borer/derivation/JsonDerivationSpec.scala b/derivation/src/test/scala/io/bullet/borer/derivation/JsonDerivationSpec.scala
index 89acdd4a..6f2c11df 100644
--- a/derivation/src/test/scala/io/bullet/borer/derivation/JsonDerivationSpec.scala
+++ b/derivation/src/test/scala/io/bullet/borer/derivation/JsonDerivationSpec.scala
@@ -172,7 +172,7 @@ object JsonDerivationSpec extends DerivationSpec(Json) {
     ArrayElem.Unsized(
       ArrayElem.Unsized(StringElem("Dog"), ArrayElem.Unsized(IntElem(12), StringElem("Fred"))),
       ArrayElem
-        .Unsized(StringElem("TheCAT"), ArrayElem.Unsized(DoubleElem(1.0f), StringElem("none"), StringElem("there"))),
+        .Unsized(StringElem("TheCAT"), ArrayElem.Unsized(DoubleElem(1.0), StringElem("none"), StringElem("there"))),
       ArrayElem.Unsized(StringElem("Dog"), ArrayElem.Unsized(IntElem(4), StringElem("Lolle"))),
       ArrayElem.Unsized(IntElem(42), BooleanElem.True))