diff --git a/tools/munger/scripts/action_gen.py b/tools/munger/scripts/action_gen.py
index 490fa54..116cd7b 100644
--- a/tools/munger/scripts/action_gen.py
+++ b/tools/munger/scripts/action_gen.py
@@ -77,7 +77,7 @@
         self.type = --ACTION_NAME--
         self.len = self.__len__()
     def show(self, prefix=''):
-        outstr += prefix + "action_--TYPE--\\n"
+        outstr = prefix + "action_--TYPE--\\n"
         outstr += --PARENT_TYPE--.show(self, prefix)
         return outstr
 """