diff --git a/core/src/main/scala/sbt/librarymanagement/CrossVersion.scala b/core/src/main/scala/sbt/librarymanagement/CrossVersion.scala
index 19e712981..4ab1b6446 100644
--- a/core/src/main/scala/sbt/librarymanagement/CrossVersion.scala
+++ b/core/src/main/scala/sbt/librarymanagement/CrossVersion.scala
@@ -331,14 +331,30 @@ trait CrossVersionFormats {
     with sbt.librarymanagement.ConstantFormats
     with sbt.librarymanagement.PatchFormats
     with sbt.librarymanagement.FullFormats =>
-  implicit lazy val CrossVersionFormat: JsonFormat[sbt.librarymanagement.CrossVersion] =
-    flatUnionFormat6[
-      sbt.librarymanagement.CrossVersion,
-      sbt.librarymanagement.Disabled,
-      sbt.librarymanagement.Disabled.type,
-      sbt.librarymanagement.Binary,
-      sbt.librarymanagement.Constant,
-      sbt.librarymanagement.Patch,
-      sbt.librarymanagement.Full
+  implicit lazy val CrossVersionFormat: JsonFormat[CrossVersion] = {
+    val format = flatUnionFormat6[
+      CrossVersion,
+      Disabled,
+      Disabled.type,
+      Binary,
+      Constant,
+      Patch,
+      Full
     ]("type")
+    // This is a hand-crafted formatter to avoid Disabled$ showing up in JSON
+    new JsonFormat[CrossVersion] {
+      override def read[J](jsOpt: Option[J], unbuilder: Unbuilder[J]): CrossVersion =
+        format.read(jsOpt, unbuilder)
+      override def write[J](obj: CrossVersion, builder: Builder[J]): Unit = {
+        if (obj == Disabled) {
+          builder.beginPreObject()
+          builder.addFieldName("type")
+          builder.writeString("Disabled")
+          builder.endPreObject()
+          builder.beginObject()
+          builder.endObject()
+        } else format.write(obj, builder)
+      }
+    }
+  }
 }
diff --git a/core/src/test/scala/sbt/librarymanagement/ModuleIdTest.scala b/core/src/test/scala/sbt/librarymanagement/ModuleIdTest.scala
index a9bab61f0..1698f317a 100644
--- a/core/src/test/scala/sbt/librarymanagement/ModuleIdTest.scala
+++ b/core/src/test/scala/sbt/librarymanagement/ModuleIdTest.scala
@@ -1,8 +1,11 @@
 package sbt.librarymanagement
 
 import sbt.internal.librarymanagement.UnitSpec
+import sjsonnew.support.scalajson.unsafe.{ Converter, CompactPrinter, Parser }
 
 class ModuleIdTest extends UnitSpec {
+  val expectedJson =
+    """{"organization":"com.acme","name":"foo","revision":"1","isChanging":false,"isTransitive":true,"isForce":false,"explicitArtifacts":[],"inclusions":[],"exclusions":[],"extraAttributes":{},"crossVersion":{"type":"Disabled"}}"""
   "Module Id" should "return cross-disabled module id as equal to a copy" in {
     ModuleID("com.acme", "foo", "1") shouldBe ModuleID("com.acme", "foo", "1")
   }
@@ -14,4 +17,15 @@ class ModuleIdTest extends UnitSpec {
     (ModuleID("com.acme", "foo", "1") cross CrossVersion.binary) shouldBe
       (ModuleID("com.acme", "foo", "1") cross CrossVersion.binary)
   }
+  it should "format itself into JSON" in {
+    import LibraryManagementCodec._
+    val json = Converter.toJson(ModuleID("com.acme", "foo", "1")).get
+    assert(CompactPrinter(json) == expectedJson)
+  }
+  it should "thaw back from JSON" in {
+    import LibraryManagementCodec._
+    val json = Parser.parseUnsafe(expectedJson)
+    val m = Converter.fromJsonUnsafe[ModuleID](json)
+    assert(m == ModuleID("com.acme", "foo", "1"))
+  }
 }