diff --git a/unipay/providers/alipay.py b/unipay/providers/alipay.py
index 215cfc7..b33d63a 100644
--- a/unipay/providers/alipay.py
+++ b/unipay/providers/alipay.py
@@ -168,7 +168,7 @@ class AlipayGateway(Gateway):
 		biz_content = {
 			"out_trade_no": payload.origin_id,
 			"refund_amount": payload.refund_amount,
-			"out_request_no": payload.out_trade_no
+			"out_request_no": payload.out_trade_no,
 			"notify_url": payload.notify_url
 		}