diff --git a/src/pretix/plugins/stripe/payment.py b/src/pretix/plugins/stripe/payment.py
index 2146358073..094499e5f1 100644
--- a/src/pretix/plugins/stripe/payment.py
+++ b/src/pretix/plugins/stripe/payment.py
@@ -556,7 +556,7 @@ class StripeMethod(BasePaymentProvider):
             # the postfix.
             return '{code} {postfix}'.format(
                 code=payment.order.code,
-                postfix=self.settings.postfix,
+                postfix=re.sub('[^a-zA-Z0-9 ]', '', str(self.settings.postfix)),
             )[:length]
         else:
             # If no custom postfix is set, we transmit the event slug and event name for backwards compatibility