diff --git a/src/type-generator.cpp b/src/type-generator.cpp
index d6d8adf313..626573af8e 100644
--- a/src/type-generator.cpp
+++ b/src/type-generator.cpp
@@ -1911,7 +1911,7 @@ writeConstructors(Output* out, Object* declarations)
 
       out->write(")\n{\n");
 
-      bool hasObjectMask = false;
+      bool hasObjectMask = strcmp(typeName(o), "singleton") == 0;
       for (MemberIterator it(o); it.hasMore();) {
         Object* m = it.next();
         if (m->type == Object::Scalar