diff --git a/modules/federation/invite2.cc b/modules/federation/invite2.cc
index 5262e68a3..1c7e9b25b 100644
--- a/modules/federation/invite2.cc
+++ b/modules/federation/invite2.cc
@@ -86,37 +86,15 @@ put__invite(client &client,
 		request["event"], event_id
 	};
 
-	char check_buf[48];
-	m::event::id check_id; switch(hash(room_version))
-	{
-		case "1"_:
-		case "2"_:
-			check_id = json::get<"event_id"_>(event)?
-				m::event::id{json::get<"event_id"_>(event)}:
-				event_id;
+	if(!json::get<"event_id"_>(event))
+		if(room_version == "1" || room_version == "2")
+			json::get<"event_id"_>(event) = event_id;
 
-			// put back the event_id that synapse stripped
-			json::get<"event_id"_>(event) = check_id;
-			assert(json::get<"event_id"_>(event) == check_id);
-			break;
-
-		case "3"_:
-			check_id = m::event::id::v3{check_buf, event};
-			break;
-
-		case "4"_:
-		case "5"_:
-		default:
-			check_id = m::event::id::v4{check_buf, event};
-			break;
-	}
-
-	if(!check_id || event_id != check_id)
+	if(!check_id(event, room_version))
 		throw m::BAD_REQUEST
 		{
-			"Claimed event_id %s does not match %s",
+			"Claimed event_id %s is incorrect.",
 			string_view{event_id},
-			string_view{check_id},
 		};
 
 	if(at<"room_id"_>(event) != room_id)
diff --git a/modules/federation/send_join.cc b/modules/federation/send_join.cc
index 28cdd4347..39d311ffc 100644
--- a/modules/federation/send_join.cc
+++ b/modules/federation/send_join.cc
@@ -63,14 +63,14 @@ put__send_join(client &client,
 
 	const m::event event
 	{
-		request
+		request, event_id
 	};
 
-	if(at<"event_id"_>(event) != event_id)
-		throw m::error
+	if(!check_id(event))
+		throw m::BAD_REQUEST
 		{
-			http::NOT_MODIFIED, "M_MISMATCH_EVENT_ID",
-			"ID of event in request body does not match path parameter."
+			"ID of event in request does not match path parameter %s",
+			string_view{event_id},
 		};
 
 	if(at<"room_id"_>(event) != room_id)
diff --git a/modules/federation/send_leave.cc b/modules/federation/send_leave.cc
index a37601e50..407172188 100644
--- a/modules/federation/send_leave.cc
+++ b/modules/federation/send_leave.cc
@@ -63,14 +63,14 @@ put__send_leave(client &client,
 
 	const m::event event
 	{
-		request
+		request, event_id
 	};
 
-	if(at<"event_id"_>(event) != event_id)
-		throw m::error
+	if(!check_id(event))
+		throw m::BAD_REQUEST
 		{
-			http::NOT_MODIFIED, "M_MISMATCH_EVENT_ID",
-			"ID of event in request body does not match path parameter."
+			"ID of event in request does not match path parameter %s",
+			string_view{event_id},
 		};
 
 	if(at<"room_id"_>(event) != room_id)