diff --git a/sqlalchemy_utils/types/encrypted.py b/sqlalchemy_utils/types/encrypted.py
index 2446348..0d28b41 100644
--- a/sqlalchemy_utils/types/encrypted.py
+++ b/sqlalchemy_utils/types/encrypted.py
@@ -28,7 +28,7 @@ class EncryptionDecryptionBaseEngine(object):
 
     def _update_key(self, key):
         if isinstance(key, six.string_types):
-            key = six.b(key)
+            key = key.encode()
         digest = hashes.Hash(hashes.SHA256(), backend=default_backend())
         digest.update(key)
         engine_key = digest.finalize()
diff --git a/tests/types/test_encrypted.py b/tests/types/test_encrypted.py
index cef9dd5..d5ca19c 100644
--- a/tests/types/test_encrypted.py
+++ b/tests/types/test_encrypted.py
@@ -139,7 +139,7 @@ class EncryptedTypeTestCase(TestCase):
         class Team(self.Base):
             __tablename__ = 'team'
             id = sa.Column(sa.Integer, primary_key=True)
-            key = sa.Column(sa.Unicode(50))
+            key = sa.Column(sa.String(50))
             name = sa.Column(EncryptedType(
                 sa.Unicode,
                 lambda: self._team_key,
@@ -181,18 +181,17 @@ class EncryptedTypeTestCase(TestCase):
     def test_lookup_key(self):
         # Add teams
         self._team_key = 'one'
-        team = self.Team(key=self._team_key, name='One')
+        team = self.Team(key=self._team_key, name=u'One')
         self.session.add(team)
-        self.session.flush()
+        self.session.commit()
         team_1_id = team.id
 
         self._team_key = 'two'
-        team = self.Team(key=self._team_key, name='Two')
+        team = self.Team(key=self._team_key)
+        team.name = u'Two'
         self.session.add(team)
-        self.session.flush()
-        team_2_id = team.id
-
         self.session.commit()
+        team_2_id = team.id
 
         # Lookup teams
         self._team_key = self.session.query(self.Team.key).filter_by(
@@ -201,22 +200,26 @@ class EncryptedTypeTestCase(TestCase):
 
         team = self.session.query(self.Team).get(team_1_id)
 
-        assert team.name == 'One'
+        assert team.name == u'One'
 
         with pytest.raises(Exception):
             self.session.query(self.Team).get(team_2_id)
 
+        self.session.expunge_all()
+
         self._team_key = self.session.query(self.Team.key).filter_by(
             id=team_2_id
         ).one()[0]
 
         team = self.session.query(self.Team).get(team_2_id)
 
-        assert team.name == 'Two'
+        assert team.name == u'Two'
 
         with pytest.raises(Exception):
             self.session.query(self.Team).get(team_1_id)
 
+        self.session.expunge_all()
+
         # Remove teams
         self.session.query(self.Team).delete()
         self.session.commit()