diff -r 06d28f03f6f4 -r c0242a51774c plcopen/plcopen.py
--- a/plcopen/plcopen.py	Wed Jan 02 18:15:31 2008 +0100
+++ b/plcopen/plcopen.py	Wed Jan 02 18:16:12 2008 +0100
@@ -465,7 +465,7 @@
             for var in variables:
                 if var.getName() == old_name:
                     vartype_content = var.getType().getContent()
-                    if vartype_content["value"] is not None and vartype_content["value"].getName() == old_type:
+                    if vartype_content["name"] == "derived" and vartype_content["value"].getName() == old_type:
                         var.setName(new_name)
                         vartype_content["value"].setName(new_type)
                         return