diff --git a/src/testdir/test_python2.vim b/src/testdir/test_python2.vim
index 42fadaa..8fa7340 100644
--- a/src/testdir/test_python2.vim
+++ b/src/testdir/test_python2.vim
@@ -73,7 +73,7 @@
 
   " Try modifying a buffer with 'nomodifiable' set
   set nomodifiable
-  call assert_fails('pydo toupper(line)', 'cannot save undo information')
+  call assert_fails('pydo toupper(line)', 'E21:')
   set modifiable
 
   " Invalid command