From 35c8684cd49eca0a472b51120896808c042c88ec Mon Sep 17 00:00:00 2001
From: Raphael Michel <mail@raphaelmichel.de>
Date: Tue, 4 Aug 2020 14:06:54 +0200
Subject: [PATCH] Prevent issues with order fees and TaxRule.zero()

---
 src/pretix/base/models/orders.py | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/pretix/base/models/orders.py b/src/pretix/base/models/orders.py
index 44f044e39a..20de183be3 100644
--- a/src/pretix/base/models/orders.py
+++ b/src/pretix/base/models/orders.py
@@ -1869,6 +1869,9 @@ class OrderFee(models.Model):
             self.tax_rate = Decimal('0.00')
 
     def save(self, *args, **kwargs):
+        if self.tax_rule and not self.tax_rule.rate and not self.tax_rule.pk:
+            self.tax_rule = None
+
         if self.tax_rate is None:
             self._calculate_tax()
         self.order.touch()