diff --git a/clientapi/routing/login.go b/clientapi/routing/login.go
index 0105f6d21..523a8e250 100644
--- a/clientapi/routing/login.go
+++ b/clientapi/routing/login.go
@@ -73,7 +73,7 @@ func Login(
 			return util.JSONResponse{
 				Code: http.StatusOK,
 				JSON: loginResponse{
-					UserID:      login.Username(),
+					UserID:      userutil.MakeUserID(login.Username(), cfg.Matrix.ServerName),
 					AccessToken: "",
 					HomeServer:  cfg.Matrix.ServerName,
 					DeviceID:    "",