diff --git a/README.md b/README.md
index a133273b25d7a7d74df412eb60be67aefea23c99..53a33747c5b31dfd7cf8534b620574c283467334 100644
--- a/README.md
+++ b/README.md
@@ -11,6 +11,9 @@ Check Info:
     * maximum connections (count)
     * current connections (count)
 
+
+**Note:** works with Cisco ASA55xx and later
+
 Sample output
 
 ![sample output](/doc/sample.png?raw=true "sample [SHORT TITLE]")