diff --git a/Lib/lua/factory.i b/Lib/lua/factory.i
new file mode 100644
index 000000000..7e605c5d5
--- /dev/null
+++ b/Lib/lua/factory.i
@@ -0,0 +1,23 @@
+/*
+	A modification of factory.swg from the generic UTL library.
+*/
+
+%include <typemaps/swigmacros.swg>
+
+%define %_factory_dispatch(Type) 
+if (!dcast) {
+  Type *dobj = dynamic_cast<Type *>($1);
+  if (dobj) {
+    dcast = 1;
+    SWIG_NewPointerObj(L, dobj, $descriptor(Type *), $owner); SWIG_arg++;
+  }   
+}%enddef
+
+%define %factory(Method,Types...)
+%typemap(out) Method {
+  int dcast = 0;
+  %formacro(%_factory_dispatch, Types)
+  if (!dcast) {
+    SWIG_NewPointerObj(L, $1, $descriptor, $owner); SWIG_arg++;
+  }
+}%enddef