diff --git a/gluon/messageboxhandler.py b/gluon/messageboxhandler.py
index 6808cb54..70079cdf 100644
--- a/gluon/messageboxhandler.py
+++ b/gluon/messageboxhandler.py
@@ -8,7 +8,7 @@ try:
     else:
         import tkinter
 except ImportError:
-    Tkinter = None
+    tkinter = None
 
 
 class MessageBoxHandler(logging.Handler):