diff --git a/src/Nest/XPack/Security/Authenticate/AuthenticateResponse.cs b/src/Nest/XPack/Security/Authenticate/AuthenticateResponse.cs
index 21cdbdc13d0..bae70d2920c 100644
--- a/src/Nest/XPack/Security/Authenticate/AuthenticateResponse.cs
+++ b/src/Nest/XPack/Security/Authenticate/AuthenticateResponse.cs
@@ -41,5 +41,8 @@ public class AuthenticateResponse : ResponseBase
 
 		[DataMember(Name = "lookup_realm")]
 		public RealmInfo LookupRealm { get; internal set; }
+
+		[DataMember(Name = "authentication_type")]
+		public string AuthenticationType { get; internal set; }
 	}
 }