diff --git a/middleware/onerror.js b/middleware/onerror.js
index 3ce9e0fc67..75bc9c4086 100644
--- a/middleware/onerror.js
+++ b/middleware/onerror.js
@@ -4,7 +4,7 @@ module.exports = async (ctx, next) => {
     try {
         await next();
     } catch (err) {
-        logger.error('Promise error: ' + err);
+        logger.error('Promise error: ' + (err instanceof Error ? err.stack : err));
         ctx.set({
             'Content-Type': 'text/html; charset=UTF-8',
         });