diff --git a/autocomplete_multi_models/models.py b/autocomplete_multi_models/models.py
index 0a50c2a92162c9a2cc310b87630a8a75f11f5f67..727f95c3e97c84df72652d709726ae60dd419e89 100644
--- a/autocomplete_multi_models/models.py
+++ b/autocomplete_multi_models/models.py
@@ -15,6 +15,7 @@ class IndexedWord(django.db.models.Model):
     occurrence = django.db.models.IntegerField(
         null=True,
         blank=True,
+        default=None,
     )
 
     def __str__(self):