diff --git a/src/testdir/test_syntax.vim b/src/testdir/test_syntax.vim
index 1969152..ca87ccf 100644
--- a/src/testdir/test_syntax.vim
+++ b/src/testdir/test_syntax.vim
@@ -428,6 +428,8 @@
   set bg=dark
   hi Normal ctermbg=12
   call assert_equal('dark', &bg)
+
+  hi Normal ctermbg=NONE
 endfunc
 
 func Test_syntax_hangs()