diff --git a/payments/models.py b/payments/models.py
index 540c021..b33c39f 100644
--- a/payments/models.py
+++ b/payments/models.py
@@ -4,6 +4,7 @@ from django.conf import settings
 from django.utils.translation import ugettext_lazy as _
 from jsonfield import JSONField
 from datetime import timedelta
+import json
 
 from ccvpn.common import get_price
 from .backends import BackendBase
@@ -103,6 +104,10 @@ class BackendData:
         """ adds a backend data key to this instance's dict """
         if not self.backend_data:
             self.backend_data = {}
+
+        if isinstance(self.backend_data, str):
+            self.backend_data = json.loads(self.backend_data) or {}
+
         if not isinstance(self.backend_data, dict):
             raise Exception("self.backend_data is not a dict (%r)" % self.backend_data)
         self.backend_data[key] = value