diff --git a/anki/collection.py b/anki/collection.py
index f430eb98c..096507d37 100644
--- a/anki/collection.py
+++ b/anki/collection.py
@@ -695,6 +695,10 @@ select id from notes where mid not in """ + ids2str(self.models.ids()))
             self.remNotes(ids)
         # for each model
         for m in self.models.all():
+            for t in m['tmpls']:
+                if t['did'] == "None":
+                    t['did'] = None
+                    problems.append(_("Fixed AnkiDroid deck override bug."))
             if m['type'] == MODEL_STD:
                 # model with missing req specification
                 if 'req' not in m: