diff --git a/easy_my_coop_ch/models/coop.py b/easy_my_coop_ch/models/coop.py
index cb30d7a..e8a3c80 100644
--- a/easy_my_coop_ch/models/coop.py
+++ b/easy_my_coop_ch/models/coop.py
@@ -23,3 +23,8 @@ class SubscriptionRequest(models.Model):
             req_fields.remove("iban")
 
         return req_fields
+
+    def check_iban(self, iban):
+        if iban:
+            return super(SubscriptionRequest, self).check_iban(iban)
+        return True