diff --git a/tcms/management/models.py b/tcms/management/models.py
index 656823131c..8143bc0b67 100755
--- a/tcms/management/models.py
+++ b/tcms/management/models.py
@@ -1,6 +1,7 @@
 # -*- coding: utf-8 -*-
 
 from django.db import models
+from django.conf import settings
 
 from tcms.core.models import TCMSActionModel
 
@@ -59,14 +60,14 @@ class Component(TCMSActionModel):
     name = models.CharField(max_length=64)
     product = models.ForeignKey(Product, related_name='component', on_delete=models.CASCADE)
     initial_owner = models.ForeignKey(
-        'auth.User',
+        settings.AUTH_USER_MODEL,
         db_column='initialowner',
         related_name='initialowner',
         null=True,
         on_delete=models.CASCADE
     )
     initial_qa_contact = models.ForeignKey(
-        'auth.User',
+        settings.AUTH_USER_MODEL,
         db_column='initialqacontact',
         related_name='initialqacontact',
         blank=True,
diff --git a/tcms/testruns/models.py b/tcms/testruns/models.py
index 6dbdc55dfb..597ee38c74 100755
--- a/tcms/testruns/models.py
+++ b/tcms/testruns/models.py
@@ -56,7 +56,7 @@ class TestRun(TCMSActionModel):
                                  through='testruns.TestRunTag',
                                  related_name='run')
 
-    cc = models.ManyToManyField('auth.User', through='testruns.TestRunCC')
+    cc = models.ManyToManyField(settings.AUTH_USER_MODEL, through='testruns.TestRunCC')
 
     class Meta:
         unique_together = ('run_id', 'product_version')
diff --git a/tcms/tests/factories.py b/tcms/tests/factories.py
index 2aacbb614c..495d2dc890 100644
--- a/tcms/tests/factories.py
+++ b/tcms/tests/factories.py
@@ -4,6 +4,7 @@
 from datetime import datetime
 
 from django.db.models import signals
+from django.conf import settings
 
 import factory
 from factory.django import DjangoModelFactory
@@ -20,7 +21,7 @@
 class UserFactory(DjangoModelFactory):
 
     class Meta:
-        model = 'auth.User'
+        model = settings.AUTH_USER_MODEL
 
     username = factory.Sequence(lambda n: 'User%d' % n)
     email = factory.LazyAttribute(lambda user: '%s@example.com' % user.username)