--- a/PLCGenerator.py	Thu Mar 13 10:20:00 2008 +0100
+++ b/PLCGenerator.py	Thu Mar 13 10:20:23 2008 +0100
@@ -118,7 +118,9 @@
             pou_program = PouProgram(pou.getname(), pouTypeNames[pou_type])
         else:
             raise PLCGenException, "Undefined pou type"
-        pou_program.GenerateInterface(pou.getinterface())
+        interface = pou.getinterface()
+        if interface is not None:
+            pou_program.GenerateInterface(interface)
         pou_program.GenerateConnectionTypes(pou)
         pou_program.GenerateProgram(pou)
         currentProgram += pou_program.GenerateSTProgram()