diff --git a/Source/Modules/lua.cxx b/Source/Modules/lua.cxx
index 002c6eb3a..9bb1374e1 100644
--- a/Source/Modules/lua.cxx
+++ b/Source/Modules/lua.cxx
@@ -73,6 +73,11 @@ void display_mapping(DOH *d) {
   }
 }
 
+extern "C" static int compareByLen(const DOH *f, const DOH *s) {
+  return Len(s) - Len(f);
+}
+
+
 /* NEW LANGUAGE NOTE:***********************************************
  most of the default options are handled by SWIG
  you can add new ones here
@@ -2064,10 +2069,6 @@ public:
     Printv(output, "\n", NIL);
   }
 
-  static int compareByLen(const DOH *f, const DOH *s) {
-    return Len(s) - Len(f);
-  }
-
   /* -----------------------------------------------------------------------------
    * closeNamespaces()
    *