diff --git a/src/testdir/test_diffmode.vim b/src/testdir/test_diffmode.vim
index 33617c9..73f944b 100644
--- a/src/testdir/test_diffmode.vim
+++ b/src/testdir/test_diffmode.vim
@@ -1,4 +1,5 @@
 " Tests for diff mode
+set belloff=all
 
 func Test_diff_fold_sync()
   enew!