diff --git a/src/testdir/test_spell.vim b/src/testdir/test_spell.vim
index 76ad12e..6bf43ac 100644
--- a/src/testdir/test_spell.vim
+++ b/src/testdir/test_spell.vim
@@ -149,6 +149,12 @@
   set nospell spelllang=en
   call assert_fails('spellinfo', 'E756:')
 
+  call assert_fails('set spelllang=foo/bar', 'E474:')
+  call assert_fails('set spelllang=foo\ bar', 'E474:')
+  call assert_fails("set spelllang=foo\\\nbar", 'E474:')
+  call assert_fails("set spelllang=foo\\\rbar", 'E474:')
+  call assert_fails("set spelllang=foo+bar", 'E474:')
+
   set enc& spell& spelllang&
   bwipe
 endfunc