diff --git a/src/testdir/test_gui.vim b/src/testdir/test_gui.vim
index 89ec3a9..6d750e0 100644
--- a/src/testdir/test_gui.vim
+++ b/src/testdir/test_gui.vim
@@ -386,6 +386,13 @@
   if has('win32')
     " Invalid font names are accepted in GTK GUI
     call assert_fails('set guifont=xa1bc23d7f', 'E596:')
+
+    " doing this four times used to cause a crash
+    set guifont=
+    set guifont=
+    set guifont=
+    set guifont=
+    set guifont=
   endif
 
   if has('xfontset')