diff --git a/specification/network/resource-manager/Microsoft.Network/stable/2019-08-01/networkSecurityGroup.json b/specification/network/resource-manager/Microsoft.Network/stable/2019-08-01/networkSecurityGroup.json
index 935b9dae7fb0..f8b8cbf92b83 100644
--- a/specification/network/resource-manager/Microsoft.Network/stable/2019-08-01/networkSecurityGroup.json
+++ b/specification/network/resource-manager/Microsoft.Network/stable/2019-08-01/networkSecurityGroup.json
@@ -659,7 +659,8 @@
             "Udp",
             "Icmp",
             "Esp",
-            "*"
+            "*",
+            "Ah"
           ],
           "x-ms-enum": {
             "name": "SecurityRuleProtocol",