diff --git a/lib/tk/dialog.rb b/lib/tk/dialog.rb
index 38ad88c9..0d91ce60 100644
--- a/lib/tk/dialog.rb
+++ b/lib/tk/dialog.rb
@@ -68,7 +68,7 @@ def create_self(keys)
     @msgframe_config = msgframe_config
 
     @bitmap  = bitmap
-    @bitmap_config = message_config
+    @bitmap_config = bitmap_config
 
     @default_button = default_button