diff --git a/DNS-API-Dev-Guide.md b/DNS-API-Dev-Guide.md
index 2731f50..394ba78 100644
--- a/DNS-API-Dev-Guide.md
+++ b/DNS-API-Dev-Guide.md
@@ -264,6 +264,8 @@ Please follow the guide: https://github.com/acmesh-official/acme.sh/wiki/DNS-API
 3. Do not use `sed -e`, which causes a problem in OS X and BSD.
 4. Do not use `sed` with labels, which causes `Label too long` problem in Solaris.
 5. Do not use `sed` with newlines (`\n`), which causes a problem in OS X and BSD.
+6. Do not use `grep -E` option.
+
 
 If you need a BSD or Solaris development environment, please head to [vmactions](https://github.com/vmactions). For example, you can use [solaris-shell](https://github.com/vmactions/shell-solaris) to get a shell environment in Solaris.