diff --git a/SC2039.md b/SC2039.md
index ff12d92..59cbafc 100644
--- a/SC2039.md
+++ b/SC2039.md
@@ -1,10 +1,10 @@
-## `#!/bin/sh` was specified, but *something* is not standard.
+## In POSIX sh, [[ ]] is undefined.
 
 The shebang indicates that the script works with `/bin/sh`, but you are using non-standard features that may not be supported.
 
-It may currently work for you, but it can or will fail on other OS, the same OS with different configurations or from different contexts (like initramfs/chroot), or different versions of the same OS, including future updates to your current system.
+It may currently work for you, but it can or will fail on other OS, the same OS with different configurations, from different contexts (like initramfs/chroot), or in different versions of the same OS, including future updates to your current system.
 
-Either declare a specific shell like `#!/usr/bin/env bash` to make sure this shell is always used, or rewrite the script in a portable way.
+Either declare a specific shell like `#!/bin/bash` or `#!/bin/dash` to make sure this shell is always used, or rewrite the script in a portable way.
 
 For help with rewrites, the Ubuntu wiki has [a list of portability issues](https://wiki.ubuntu.com/DashAsBinSh) that broke people's `#!/bin/sh` scripts when Ubuntu switched from Bash to Dash. ShellCheck may not warn about all these issues.