diff --git a/src/Interop/CSharpDafnyModel.dfy b/src/Interop/CSharpDafnyModel.dfy
index 95808888..5f60dfe9 100644
--- a/src/Interop/CSharpDafnyModel.dfy
+++ b/src/Interop/CSharpDafnyModel.dfy
@@ -13,6 +13,7 @@ module {:extern "Microsoft.Dafny"} {:compile false} Microsoft.Dafny {
   class {:extern} {:compile false} VisibilityScope {}
   class {:extern} {:compile false} ErrorReporter {}
   class {:extern} {:compile false} TypeConstraint {}
+  trait {:extern} {:compile false} {:termination false} Cloner {}
 
   class {:extern} {:compile false} Resolver {}
   class {:extern "Resolver.TypeConstraint"} Resolver__TypeConstraint {}