diff --git a/Lib/idlelib/debugger_r.py b/Lib/idlelib/debugger_r.py
index 01a3bd2..0e6dcfb 100644
--- a/Lib/idlelib/debugger_r.py
+++ b/Lib/idlelib/debugger_r.py
@@ -157,7 +157,7 @@
     #----------called by a DictProxy----------
 
     def dict_keys(self, did):
-        raise NotImplemented("dict_keys not public or pickleable")
+        raise NotImplementedError("dict_keys not public or pickleable")
 ##         dict = dicttable[did]
 ##         return dict.keys()