diff --git a/etherpadlite/migrations/0006_auto_20191008_1135.py b/etherpadlite/migrations/0006_auto_20191008_1135.py
new file mode 100644
index 0000000000000000000000000000000000000000..97a786b5ca9e3cf4da0a749a7a3aaf5d82cb2387
--- /dev/null
+++ b/etherpadlite/migrations/0006_auto_20191008_1135.py
@@ -0,0 +1,18 @@
+# Generated by Django 2.2.2 on 2019-10-08 11:35
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('etherpadlite', '0005_auto_20190416_0918'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='padauthor',
+            name='group',
+            field=models.ManyToManyField(blank=True, related_name='authors', to='etherpadlite.PadGroup'),
+        ),
+    ]
diff --git a/etherpadlite/models.py b/etherpadlite/models.py
index 09de377b9afe9b76bcc5d3149babc594a2bf0c4c..cf8c433953cf82baeb7c2a964db82f31f902aa2a 100755
--- a/etherpadlite/models.py
+++ b/etherpadlite/models.py
@@ -111,7 +111,6 @@ class PadAuthor(models.Model):
     group = models.ManyToManyField(
         PadGroup,
         blank=True,
-        null=True,
         related_name='authors'
     )