diff --git a/backend/members/models.py b/backend/members/models.py
index 99ad5192..9a16d862 100644
--- a/backend/members/models.py
+++ b/backend/members/models.py
@@ -56,7 +56,7 @@ class Member(models.Model):
     objects = MemberManager()
 
     def clean(self):
-        members = self.objects.exclude(id=self.id)
+        members = self.__class__.objects.exclude(id=self.id)
         if members.filter(user=self.user, project=self.project).exists():
             message = 'This user is already assigned to a role in this project.'
             raise ValidationError(message)
diff --git a/backend/members/tests.py b/backend/members/tests.py
index e2e91cca..bc452827 100644
--- a/backend/members/tests.py
+++ b/backend/members/tests.py
@@ -1,6 +1,9 @@
 from django.conf import settings
+from django.test import TestCase
+from django.core.exceptions import ValidationError
 from rest_framework import status
 from rest_framework.reverse import reverse
+from model_mommy import mommy
 
 from roles.models import Role
 from members.models import Member
@@ -116,9 +119,6 @@ class TestMemberFilter(CRUDMixin):
 
 class TestMemberManager(CRUDMixin):
 
-    def setUp(self):
-        pass
-
     def test_has_role(self):
         project = prepare_project()
         admin = project.users[0]
@@ -129,3 +129,12 @@ class TestMemberManager(CRUDMixin):
         ]
         for role, expect in expected:
             self.assertEqual(Member.objects.has_role(project.item, admin, role), expect)
+
+
+class TestMember(TestCase):
+
+    def test_clean(self):
+        member = mommy.make('Member')
+        same_user = Member(project=member.project, user=member.user, role=member.role)
+        with self.assertRaises(ValidationError):
+            same_user.clean()