diff --git a/models/payment.py b/models/payment.py
index 23030ca54..5e1b3bb22 100644
--- a/models/payment.py
+++ b/models/payment.py
@@ -323,7 +323,7 @@ def customer_reference(self):
         if self.currency == "EUR":
             order_id = f"{event_year()}{self.id:08d}"
             order_check_digits = mod_97_10.calc_check_digits(f"{order_id}RF")
-            customer_reference =  f"RF{order_check_digits}{order_id}"
+            customer_reference = f"RF{order_check_digits}{order_id}"
             assert iso11649.validate(customer_reference)
             return customer_reference
         else: