diff --git a/src/testdir/test_functions.vim b/src/testdir/test_functions.vim
index 9eae10d..68dbb0a 100644
--- a/src/testdir/test_functions.vim
+++ b/src/testdir/test_functions.vim
@@ -2679,8 +2679,8 @@
     else
       let cmd = "ls"
     endif
-    call assert_fails('call term_start("' .. cmd .. '", #{term_finish: "close"})', 'E475:')
-    unlet g:terminal_ansi_colors
+    call assert_fails('call term_start("' .. cmd .. '", #{term_finish: "close"'
+        \ .. ', ansi_colors: range(16)})', 'E475:')
   endif
 
   " type()