diff --git a/backend/sophon/core/migrations/0006_alter_researchgroup_members.py b/backend/sophon/core/migrations/0006_alter_researchgroup_members.py
new file mode 100644
index 0000000..6bb2ad3
--- /dev/null
+++ b/backend/sophon/core/migrations/0006_alter_researchgroup_members.py
@@ -0,0 +1,20 @@
+# Generated by Django 3.2.7 on 2021-10-20 17:33
+
+from django.conf import settings
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
+        ('core', '0005_auto_20211016_0136'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='researchgroup',
+            name='members',
+            field=models.ManyToManyField(blank=True, help_text='The users who belong to this group.', related_name='is_a_member_of',
+                                         to=settings.AUTH_USER_MODEL),
+        ),
+    ]
diff --git a/backend/sophon/core/models.py b/backend/sophon/core/models.py
index db9e108..c843abc 100644
--- a/backend/sophon/core/models.py
+++ b/backend/sophon/core/models.py
@@ -338,7 +338,7 @@ class ResearchGroup(SophonGroupModel):
         User,
         help_text="The users who belong to this group.",
         related_name="is_a_member_of",
-        blank=True, null=True,
+        blank=True,
     )
 
     owner = models.ForeignKey(