diff --git a/dnsapi.md b/dnsapi.md
index e24c8e4..6b49bb8 100644
--- a/dnsapi.md
+++ b/dnsapi.md
@@ -2734,6 +2734,8 @@ Please report any issue to [https://github.com/acmesh-official/acme.sh/issues/37
 
 ## 137. Use ISPMan domain API
 
+!!! IMPORTANT: Make sure the verson of ISPMan supports TXT records !!!
+
 The `dns_ispman.sh` api Adds & Deletes domain TXT records by authenticating into the [ISPMan](http://ispman.sourceforge.net/) Customer Control Panel and executing HTTP POST & GET requests.
 
 The `dns_ispman.sh` api requires your `<domain>` and `<passwd>` for authentication: