diff -r adc79fc44079 -r 9d0cb01312f0 dialogs/BlockPreviewDialog.py
--- a/dialogs/BlockPreviewDialog.py	Thu Sep 26 20:47:36 2013 +0900
+++ b/dialogs/BlockPreviewDialog.py	Fri Sep 27 09:32:39 2013 +0900
@@ -177,7 +177,7 @@
         
         # Add POU name to variable list if POU is a function 
         returntype = self.Controller.GetEditedElementInterfaceReturnType(
-                                                            self.TagName)
+                                                            self.TagName)[0]
         if returntype is not None:
             self.VariableList[
                 self.Controller.GetEditedElementName(self.TagName)] = \