diff --git a/server/core/service.c b/server/core/service.c
index d44805132..da1053402 100644
--- a/server/core/service.c
+++ b/server/core/service.c
@@ -1606,6 +1606,7 @@ service_update(SERVICE *service, char *router, char *user, char *auth)
  */
 int service_refresh_users(SERVICE *service)
 {
+    ss_dassert(service);
     int ret = 1;
 
     if (spinlock_acquire_nowait(&service->spin))
diff --git a/server/modules/protocol/MySQL/MySQLBackend/mysql_backend.c b/server/modules/protocol/MySQL/MySQLBackend/mysql_backend.c
index e03761cf7..9d70cc3e3 100644
--- a/server/modules/protocol/MySQL/MySQLBackend/mysql_backend.c
+++ b/server/modules/protocol/MySQL/MySQLBackend/mysql_backend.c
@@ -358,8 +358,11 @@ static void handle_error_response(DCB *dcb, GWBUF *buffer)
              errcode == ER_DBACCESS_DENIED_ERROR ||
              errcode == ER_ACCESS_DENIED_NO_PASSWORD_ERROR)
     {
-        // Authentication failed, reload users
-        service_refresh_users(dcb->service);
+        if (dcb->session->state != SESSION_STATE_DUMMY)
+        {
+            // Authentication failed, reload users
+            service_refresh_users(dcb->service);
+        }
     }
 }