diff --git a/lib/ansible/modules/cloud/azure/azure_rm_appgateway.py b/lib/ansible/modules/cloud/azure/azure_rm_appgateway.py
index 8b1c55b121..aa05b99652 100644
--- a/lib/ansible/modules/cloud/azure/azure_rm_appgateway.py
+++ b/lib/ansible/modules/cloud/azure/azure_rm_appgateway.py
@@ -294,6 +294,7 @@ options:
             authentication_certificates:
                 description:
                     - List of references to application gateway authentication certificates.
+                    - Applicable only when C(cookie_based_affinity) is enabled, otherwise quietly ignored.
                 suboptions:
                     id:
                         description: