diff --git a/unipay/init.py b/unipay/init.py
index 404ba22..fe47394 100644
--- a/unipay/init.py
+++ b/unipay/init.py
@@ -8,7 +8,7 @@ from .paylog import PaymentLog
 CONF = {
 	"wechat": {
 		"mchid": os.getenv("WXP_MCHID",""),
-		"appid": os.getenv("WXP_APPID", "")
+		"appid": os.getenv("WXP_APPID", ""),
 		"cert_serial_no": os.getenv("WXP_SERIAL",""),
 		"private_key_pem": open(os.getenv("WXP_PRIVKEY","./merchant_private_key.pem"),"rb").read(),
 		"api_v3_key": os.getenv("WXP_API_V3_KEY","").encode()