diff --git a/lib/ansible/modules/windows/win_firewall_rule.py b/lib/ansible/modules/windows/win_firewall_rule.py
index ec74b1b6ed9..cd47cbb32dd 100644
--- a/lib/ansible/modules/windows/win_firewall_rule.py
+++ b/lib/ansible/modules/windows/win_firewall_rule.py
@@ -67,6 +67,7 @@ options:
       - The local port this rule applies to.
       - Set to C(any) to apply to all local ports.
       - Defaults to C(any) when creating a new rule.
+      - Must have I(protocol) set
     type: str
   remoteport:
     description: