diff --git a/panko/storage/impl_sqlalchemy.py b/panko/storage/impl_sqlalchemy.py
index e5bbeb4b..521e268e 100644
--- a/panko/storage/impl_sqlalchemy.py
+++ b/panko/storage/impl_sqlalchemy.py
@@ -146,15 +146,13 @@ class Connection(base.Connection):
             engine.execute(table.delete())
         engine.dispose()
 
-    def _get_or_create_event_type(self, event_type, session=None):
+    def _get_or_create_event_type(self, event_type, session):
         """Check if an event type with the supplied name is already exists.
 
         If not, we create it and return the record. This may result in a flush.
         """
         try:
-            if session is None:
-                session = self._engine_facade.get_session()
-            with session.begin(subtransactions=True):
+            with session.begin(nested=True):
                 et = session.query(models.EventType).filter(
                     models.EventType.desc == event_type).first()
                 if not et:
diff --git a/panko/tests/functional/storage/test_impl_sqlalchemy.py b/panko/tests/functional/storage/test_impl_sqlalchemy.py
index 5bc07417..dd64b844 100644
--- a/panko/tests/functional/storage/test_impl_sqlalchemy.py
+++ b/panko/tests/functional/storage/test_impl_sqlalchemy.py
@@ -43,22 +43,32 @@ class EventTypeTest(tests_db.TestBase):
     # EventType is a construct specific to sqlalchemy
     # Not applicable to other drivers.
 
+    def setUp(self):
+        super(EventTypeTest, self).setUp()
+        self.session = self.conn._engine_facade.get_session()
+        self.session.begin()
+
     def test_event_type_exists(self):
-        et1 = self.conn._get_or_create_event_type("foo")
+        et1 = self.conn._get_or_create_event_type("foo", self.session)
         self.assertTrue(et1.id >= 0)
-        et2 = self.conn._get_or_create_event_type("foo")
+        et2 = self.conn._get_or_create_event_type("foo", self.session)
         self.assertEqual(et2.id, et1.id)
         self.assertEqual(et2.desc, et1.desc)
 
     def test_event_type_unique(self):
-        et1 = self.conn._get_or_create_event_type("foo")
+        et1 = self.conn._get_or_create_event_type("foo", self.session)
         self.assertTrue(et1.id >= 0)
-        et2 = self.conn._get_or_create_event_type("blah")
+        et2 = self.conn._get_or_create_event_type("blah", self.session)
         self.assertNotEqual(et1.id, et2.id)
         self.assertNotEqual(et1.desc, et2.desc)
         # Test the method __repr__ returns a string
         self.assertTrue(reprlib.repr(et2))
 
+    def tearDown(self):
+        self.session.rollback()
+        self.session.close()
+        super(EventTypeTest, self).tearDown()
+
 
 @tests_db.run_with('sqlite', 'mysql', 'pgsql')
 class EventTest(tests_db.TestBase):