diff --git a/registration/views.py b/registration/views.py
index b63ef76..30b9eef 100644
--- a/registration/views.py
+++ b/registration/views.py
@@ -480,8 +480,8 @@ class PaymentUpdateView(LoginRequiredMixin, UpdateView):
         if self.request.user.registration.participates:
             if old_instance.valid is not False:
                 raise PermissionDenied(_("This payment is already valid or pending validation."))
-            else:
-                form.instance.valid = None
+        if old_instance.valid is False:
+            form.instance.valid = None
         if old_instance.receipt:
             old_instance.receipt.delete()
             old_instance.save()