diff --git a/runtime/syntax/testdir/input/sh_13.sh b/runtime/syntax/testdir/input/sh_13.sh
index a81c0a4..18fd0d1 100644
--- a/runtime/syntax/testdir/input/sh_13.sh
+++ b/runtime/syntax/testdir/input/sh_13.sh
@@ -1,3 +1,4 @@
+#!/bin/dash
 # Issue #17026 (bash highlighting requires space after $())
 # https://github.com/vim/vim/issues/17026#issuecomment-2774112284