diff --git a/src/testdir/test_modeline.vim b/src/testdir/test_modeline.vim
index f02c68c..3bde58d 100644
--- a/src/testdir/test_modeline.vim
+++ b/src/testdir/test_modeline.vim
@@ -1,9 +1,12 @@
 " Tests for parsing the modeline.
 
 func Test_modeline_invalid()
-  " This was reading before allocated memory.
+  " This was reading allocated memory in the past.
   call writefile(['vi:0', 'nothing'], 'Xmodeline')
+  let modeline = &modeline
+  set modeline
   call assert_fails('split Xmodeline', 'E518:')
+  let &modeline = modeline
   bwipe!
   call delete('Xmodeline')
 endfunc