diff --git a/mayan/apps/acls/classes.py b/mayan/apps/acls/classes.py
index 60acb4bbfa..e736faa4db 100644
--- a/mayan/apps/acls/classes.py
+++ b/mayan/apps/acls/classes.py
@@ -12,6 +12,12 @@ class ModelPermission(object):
     _inheritances = {}
     _registry = {}
 
+    @classmethod
+    def deregister(cls, model):
+        cls._registry.pop(model, None)
+        # TODO: Find method to revert the add_to_class('acls'...)
+        # delattr doesn't work.
+
     @classmethod
     def register(cls, model, permissions):
         from django.contrib.contenttypes.fields import GenericRelation
diff --git a/mayan/apps/acls/tests/mixins.py b/mayan/apps/acls/tests/mixins.py
index 7bc0d970c1..bf72fe56f9 100644
--- a/mayan/apps/acls/tests/mixins.py
+++ b/mayan/apps/acls/tests/mixins.py
@@ -36,10 +36,6 @@ class ACLTestMixin(PermissionTestMixin, RoleTestMixin, TestModelTestMixin):
     auto_create_test_role = True
     auto_create_test_object = False
 
-    def _create_test_acl(self):
-        self.test_acl = AccessControlList.objects.create(
-            content_object=self.test_object, role=self.test_role
-        )
 
     def setUp(self):
         super(ACLTestMixin, self).setUp()
@@ -49,6 +45,22 @@ class ACLTestMixin(PermissionTestMixin, RoleTestMixin, TestModelTestMixin):
         if self.auto_create_test_object:
             self._setup_test_object()
 
+    def tearDown(self):
+        # Deregister the permissions of the ephimeral test models
+        # this avoids their Content Type from being looked up
+        # in subsequent tests where they don't exists due to the database
+        # transaction rollback.
+        for model in self._test_models:
+            ModelPermission.deregister(model=model)
+            self._test_models.remove(model)
+
+        super(ACLTestMixin, self).tearDown()
+
+    def _create_test_acl(self):
+        self.test_acl = AccessControlList.objects.create(
+            content_object=self.test_object, role=self.test_role
+        )
+
     def _inject_test_object_content_type(self):
         self.test_object_content_type = ContentType.objects.get_for_model(
             model=self.test_object
diff --git a/mayan/apps/acls/tests/test_classes.py b/mayan/apps/acls/tests/test_classes.py
index 483f0feb57..f1ab062709 100644
--- a/mayan/apps/acls/tests/test_classes.py
+++ b/mayan/apps/acls/tests/test_classes.py
@@ -5,7 +5,7 @@ from mayan.apps.common.tests import BaseTestCase
 from ..classes import ModelPermission
 
 
-class ModelpermissionTestCase(BaseTestCase):
+class ModelPermissionTestCase(BaseTestCase):
     def test_model_permission_get_classes_as_content_type(self):
         self.assertNotEqual(
             ModelPermission.get_classes(as_content_type=True).count(), 0
diff --git a/mayan/apps/common/tests/mixins.py b/mayan/apps/common/tests/mixins.py
index 788fcc7a5d..ce1f198bcf 100644
--- a/mayan/apps/common/tests/mixins.py
+++ b/mayan/apps/common/tests/mixins.py
@@ -283,11 +283,13 @@ class TempfileCheckTestCasekMixin(object):
 
 
 class TestModelTestMixin(object):
+    _test_models = []
+
     def _create_test_model(self, fields=None, model_name='TestModel', options=None):
 
         if connection.vendor == 'mysql':
             self.skipTest(
-                reason='MySQL doesn\t support schema changes inside an '
+                reason='MySQL doesn\'t support schema changes inside an '
                 'atomic block.'
             )
 
@@ -340,6 +342,7 @@ class TestModelTestMixin(object):
             )
 
         setattr(self, model_name, TestModel)
+        self._test_models.append(TestModel)
 
         with connection.schema_editor() as schema_editor:
             schema_editor.create_model(model=TestModel)