diff --git a/app.py b/app.py
index e681df2f..2595f64c 100755
--- a/app.py
+++ b/app.py
@@ -1602,7 +1602,7 @@ def calculate_subscription_price():
         data = request.get_json()
         to_plan = data.get('to_plan')
         to_cycle = data.get('to_cycle')
-        promo_code = data.get('promo_code', '').strip() or None
+        promo_code = (data.get('promo_code') or '').strip() or None
 
         if not to_plan or not to_cycle:
             return jsonify({'success': False, 'error': '参数不完整'}), 400
@@ -1638,7 +1638,7 @@ def create_payment_order():
         data = request.get_json()
         plan_name = data.get('plan_name')
         billing_cycle = data.get('billing_cycle')
-        promo_code = data.get('promo_code', '').strip() or None
+        promo_code = (data.get('promo_code') or '').strip() or None
 
         if not plan_name or not billing_cycle:
             return jsonify({'success': False, 'error': '参数不完整'}), 400