Fix nit.
diff --git a/Lib/idlelib/EditorWindow.py b/Lib/idlelib/EditorWindow.py
index 3b7bb6d..d77f0a4 100644
--- a/Lib/idlelib/EditorWindow.py
+++ b/Lib/idlelib/EditorWindow.py
@@ -60,7 +60,7 @@
             pass
         else:
             file = None
-            descr = os.path.splitext(filename), None, imp.PY_SOURCE
+            descr = os.path.splitext(filename)[1], None, imp.PY_SOURCE
     return file, filename, descr
 
 class EditorWindow(object):