diff --git a/src/testdir/test_cmdline.vim b/src/testdir/test_cmdline.vim
index 77965b3..2289c34 100644
--- a/src/testdir/test_cmdline.vim
+++ b/src/testdir/test_cmdline.vim
@@ -3413,4 +3413,9 @@
   call assert_equal('yes', caught)
 endfunc
 
+func Test_long_error_message()
+  " the error should be truncated, not overrun IObuff
+  silent! norm Q00000000000000     000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000                                                                                                                                                                                                                        
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab