diff --git a/modoboa/relaydomains/factories.py b/modoboa/relaydomains/factories.py
index b6626d4d8..ad5182e23 100644
--- a/modoboa/relaydomains/factories.py
+++ b/modoboa/relaydomains/factories.py
@@ -28,7 +28,7 @@ class RelayDomainFactory(PermissionFactory):
         model = models.RelayDomain
         django_get_or_create = ("domain", )
 
-    domain = factory.SubFactory(DomainFactory, type="relaydomain")
     target_host = "external.host.tld"
+    domain = factory.SubFactory(DomainFactory)
     verify_recipients = True
     service = factory.SubFactory(ServiceFactory)
diff --git a/modoboa/relaydomains/forms.py b/modoboa/relaydomains/forms.py
index a656011ce..7312cc329 100644
--- a/modoboa/relaydomains/forms.py
+++ b/modoboa/relaydomains/forms.py
@@ -45,6 +45,9 @@ class RelayDomainFormGeneral(forms.ModelForm):
         """Custom save method."""
         domain = kwargs.get("domain")
         instance = super(RelayDomainFormGeneral, self).save(commit=False)
+        if instance.domain and instance.domain.type == "domain":
+            # Avoid new creation if domain type has been changed.
+            return None
         if domain:
             instance.domain = domain
         instance.save()
diff --git a/modoboa/relaydomains/handlers.py b/modoboa/relaydomains/handlers.py
index a9bd873c0..badc45634 100644
--- a/modoboa/relaydomains/handlers.py
+++ b/modoboa/relaydomains/handlers.py
@@ -41,7 +41,7 @@ def clean_domain(sender, instance, **kwargs):
         return
     has_relaydom = hasattr(instance, "relaydomain")
     if instance.type == "domain" and has_relaydom:
-        models.RelayDomain.objects.filter(domain=instance).delete()
+        instance.relaydomain.delete()
     elif instance.type == "relaydomain" and not has_relaydom:
         # Make sure to create a RelayDomain instance since we can't do it
         # at form level...
diff --git a/modoboa/relaydomains/tests.py b/modoboa/relaydomains/tests.py
index b815d945a..5805299cf 100644
--- a/modoboa/relaydomains/tests.py
+++ b/modoboa/relaydomains/tests.py
@@ -14,13 +14,13 @@ from modoboa.lib.test_utils import MapFilesTestCaseMixin
 from modoboa.limits import utils as limits_utils
 
 from .factories import RelayDomainFactory
-from .models import RelayDomain, Service
+from . import models
 
 
 class Operations(object):
 
     def _create_relay_domain(self, name, status=200):
-        srv, created = Service.objects.get_or_create(name='dummy')
+        srv, created = models.Service.objects.get_or_create(name='dummy')
         values = {
             "name": name, "create_dom_admin": False, "type": "relaydomain",
             "target_host": "external.host.tld", "service": srv.id,
@@ -32,7 +32,7 @@ class Operations(object):
         )
 
     def _relay_domain_alias_operation(self, optype, rdomain, name, status=200):
-        rdom = RelayDomain.objects.get(domain__name=rdomain)
+        rdom = models.RelayDomain.objects.get(domain__name=rdomain)
         values = {
             "name": rdom.domain.name, "target_host": rdom.target_host,
             "type": "relaydomain", "service": rdom.service.id
@@ -65,6 +65,8 @@ class RelayDomainsTestCase(ModoTestCase, Operations):
         super(RelayDomainsTestCase, cls).setUpTestData()
         admin_factories.populate_database()
         cls.rdom = RelayDomainFactory(domain__name="relaydomain.tld")
+        cls.rdom.domain.type = "relaydomain"
+        cls.rdom.domain.save()
         admin_factories.DomainAliasFactory(
             name="relaydomainalias.tld", target=cls.rdom.domain)
         admin_factories.MailboxFactory(
@@ -91,7 +93,7 @@ class RelayDomainsTestCase(ModoTestCase, Operations):
         FIXME: add a check for domain alias.
         """
         self._create_relay_domain('relaydomain1.tld')
-        rdom = RelayDomain.objects.get(domain__name='relaydomain1.tld')
+        rdom = models.RelayDomain.objects.get(domain__name='relaydomain1.tld')
         self.assertEqual(rdom.target_host, 'external.host.tld')
         self.assertEqual(rdom.service.name, 'dummy')
         self.assertEqual(rdom.domain.enabled, True)
@@ -138,16 +140,16 @@ class RelayDomainsTestCase(ModoTestCase, Operations):
         Rename 'relaydomain.tld' domain to 'relaydomain.org'
         """
         values = {
-            'name': "relaydomain.org", "target_host": self.rdom.target_host,
+            "name": "relaydomain.org", "target_host": self.rdom.target_host,
             "type": "relaydomain", "enabled": True,
             "service": self.rdom.service.id
         }
         self.ajax_post(
-            reverse('admin:domain_change',
+            reverse("admin:domain_change",
                     args=[self.rdom.domain.id]),
             values
         )
-        RelayDomain.objects.get(domain__name='relaydomain.org')
+        models.RelayDomain.objects.get(domain__name='relaydomain.org')
 
     def test_relaydomain_domain_switch(self):
         """Check domain <-> relaydomain transitions."""
@@ -156,12 +158,13 @@ class RelayDomainsTestCase(ModoTestCase, Operations):
             "name": "relaydomain.tld",
             "type": "domain",
             "enabled": True,
+            "target_host": self.rdom.target_host,
+            "service": self.rdom.service.pk
         }
         self.ajax_post(
-            reverse('admin:domain_change', args=[domain.pk]), values)
+            reverse("admin:domain_change", args=[domain.pk]), values)
         self.assertFalse(
-            RelayDomain.objects.filter(
-                domain__name="relaydomain.tld").exists())
+            models.RelayDomain.objects.filter(domain=domain).exists())
         self.assertEqual(
             admin_models.Domain.objects.get(name="relaydomain.tld").type,
             "domain")
@@ -176,7 +179,7 @@ class RelayDomainsTestCase(ModoTestCase, Operations):
             admin_models.Domain.objects.get(name="relaydomain.tld").type,
             "relaydomain")
         self.assertTrue(
-            RelayDomain.objects.filter(
+            models.RelayDomain.objects.filter(
                 domain__name="relaydomain.tld").exists())
 
     def test_edit_relaydomainalias(self):
@@ -205,16 +208,16 @@ class RelayDomainsTestCase(ModoTestCase, Operations):
                     args=[self.rdom.domain.id]),
             {}
         )
-        with self.assertRaises(RelayDomain.DoesNotExist):
-            RelayDomain.objects.get(domain__name='relaydomain.tld')
+        with self.assertRaises(models.RelayDomain.DoesNotExist):
+            models.RelayDomain.objects.get(domain__name='relaydomain.tld')
 
     def test_delete_relaydomainalias(self):
         """Test the removal of a relay domain alias."""
         self._relay_domain_alias_operation(
             'del', self.rdom.domain.name, 'relaydomainalias.tld'
         )
-        with self.assertRaises(RelayDomain.DoesNotExist):
-            RelayDomain.objects.get(domain__name='relaydomainalias.tld')
+        with self.assertRaises(models.RelayDomain.DoesNotExist):
+            models.RelayDomain.objects.get(domain__name='relaydomainalias.tld')
 
     def test_alias_on_relaydomain(self):
         """Create an alias on a relay domain."""