diff --git a/compile/interface/src/main/scala/xsbt/Compat.scala b/compile/interface/src/main/scala/xsbt/Compat.scala
index 9f9fb247c..a4859275d 100644
--- a/compile/interface/src/main/scala/xsbt/Compat.scala
+++ b/compile/interface/src/main/scala/xsbt/Compat.scala
@@ -107,8 +107,8 @@ abstract class Compat {
     }
     lazy val AnyValClass = global.rootMirror.getClassIfDefined("scala.AnyVal")
 
-    def isAnyValSubtype(sym: Symbol): Boolean = sym.isNonBottomSubClass(AnyValClass)
-
+    def isDerivedValueClass(sym: Symbol): Boolean =
+      sym.isNonBottomSubClass(AnyValClass) && !definitions.ScalaValueClasses.contains(sym)
   }
 
   object MacroExpansionOf {
diff --git a/compile/interface/src/main/scala/xsbt/ExtractAPI.scala b/compile/interface/src/main/scala/xsbt/ExtractAPI.scala
index 7a0a78b2c..011479be6 100644
--- a/compile/interface/src/main/scala/xsbt/ExtractAPI.scala
+++ b/compile/interface/src/main/scala/xsbt/ExtractAPI.scala
@@ -205,14 +205,14 @@ class ExtractAPI[GlobalType <: CallbackGlobal](val global: GlobalType,
 
       val hasValueClassAsParameter: Boolean = {
         import MirrorHelper._
-        s.asMethod.paramss.flatten map (_.info) exists (t => isAnyValSubtype(t.typeSymbol))
+        s.asMethod.paramss.flatten map (_.info) exists (t => isDerivedValueClass(t.typeSymbol))
       }
 
       def hasValueClassAsReturnType(tpe: Type): Boolean = tpe match {
         case PolyType(_, base) => hasValueClassAsReturnType(base)
         case MethodType(_, resultType) => hasValueClassAsReturnType(resultType)
         case Nullary(resultType) => hasValueClassAsReturnType(resultType)
-        case resultType => isAnyValSubtype(resultType.typeSymbol)
+        case resultType => isDerivedValueClass(resultType.typeSymbol)
       }
 
       val inspectPostErasure = hasValueClassAsParameter || hasValueClassAsReturnType(viewer(in).memberInfo(s))