diff --git a/src/testdir/test_vim9_func.vim b/src/testdir/test_vim9_func.vim
index 0fd2892..e1b3b7f 100644
--- a/src/testdir/test_vim9_func.vim
+++ b/src/testdir/test_vim9_func.vim
@@ -113,6 +113,7 @@
   call CheckDefFailure(['TakesOneArg()'], 'E119:')
   call CheckDefFailure(['TakesOneArg(11, 22)'], 'E118:')
   call CheckDefFailure(['bufnr(xxx)'], 'E1001:')
+  call CheckScriptFailure(['def Func(Ref: func(s: string))'], 'E475:')
 enddef
 
 " Default arg and varargs