diff --git a/lib/wx_pay/service.rb b/lib/wx_pay/service.rb
index f3ff1ae..b61d4b9 100644
--- a/lib/wx_pay/service.rb
+++ b/lib/wx_pay/service.rb
@@ -60,18 +60,17 @@ module WxPay
 
     GENERATE_JS_PAY_REQ_REQUIRED_FIELDS = [:prepayid, :noncestr]
     def self.generate_js_pay_req(params, options = {})
+      check_required_options(params, GENERATE_JS_PAY_REQ_REQUIRED_FIELDS)
+
       params = {
         appId: options.delete(:appid) || WxPay.appid,
-        package: "prepay_id=#{params[:prepayid]}",
-        nonceStr: params[:noncestr],
+        package: "prepay_id=#{params.delete(:prepayid)}",
+        nonceStr: params.delete(:noncestr),
         timeStamp: Time.now.to_i.to_s,
         signType: 'MD5'
       }.merge(params)
 
-      check_required_options(params, GENERATE_JS_PAY_REQ_REQUIRED_FIELDS)
-
       params[:paySign] = WxPay::Sign.generate(params)
-
       params
     end
 
--
libgit2 0.21.0