diff --git a/mistral/api/controllers/v2/types.py b/mistral/api/controllers/v2/types.py
index f656d7639..2f0efac52 100644
--- a/mistral/api/controllers/v2/types.py
+++ b/mistral/api/controllers/v2/types.py
@@ -35,8 +35,8 @@ class ListType(wtypes.UserType):
         """
         items = [v.strip().lower() for v in six.text_type(value).split(',')]
 
-        # filter() to remove empty items.
-        return filter(None, items)
+        # remove empty items.
+        return [x for x in items if x]
 
     @staticmethod
     def frombasetype(value):
diff --git a/mistral/tests/unit/api/v2/test_actions.py b/mistral/tests/unit/api/v2/test_actions.py
index c7238fa32..0378f9c75 100644
--- a/mistral/tests/unit/api/v2/test_actions.py
+++ b/mistral/tests/unit/api/v2/test_actions.py
@@ -325,7 +325,7 @@ class TestActionsController(base.FunctionalTest):
 
         self.assertIn(
             "Length of sort_keys must be equal or greater than sort_dirs",
-            resp.body
+            resp.body.decode()
         )
 
     def test_get_all_pagination_unknown_direction(self):
@@ -336,4 +336,4 @@ class TestActionsController(base.FunctionalTest):
 
         self.assertEqual(400, resp.status_int)
 
-        self.assertIn("Unknown sort direction", resp.body)
+        self.assertIn("Unknown sort direction", resp.body.decode())
diff --git a/mistral/tests/unit/api/v2/test_executions.py b/mistral/tests/unit/api/v2/test_executions.py
index 92556a80c..f8e382253 100644
--- a/mistral/tests/unit/api/v2/test_executions.py
+++ b/mistral/tests/unit/api/v2/test_executions.py
@@ -296,7 +296,7 @@ class TestExecutionsController(base.FunctionalTest):
 
         self.assertIn(
             "Length of sort_keys must be equal or greater than sort_dirs",
-            resp.body
+            resp.body.decode()
         )
 
     def test_get_all_pagination_unknown_direction(self):
@@ -307,4 +307,4 @@ class TestExecutionsController(base.FunctionalTest):
 
         self.assertEqual(400, resp.status_int)
 
-        self.assertIn("Unknown sort direction", resp.body)
+        self.assertIn("Unknown sort direction", resp.body.decode())
diff --git a/mistral/tests/unit/api/v2/test_workflows.py b/mistral/tests/unit/api/v2/test_workflows.py
index 6a30a11c8..ffaba6218 100644
--- a/mistral/tests/unit/api/v2/test_workflows.py
+++ b/mistral/tests/unit/api/v2/test_workflows.py
@@ -420,7 +420,7 @@ class TestWorkflowsController(base.FunctionalTest):
 
         self.assertIn(
             "Length of sort_keys must be equal or greater than sort_dirs",
-            resp.body
+            resp.body.decode()
         )
 
     def test_get_all_pagination_unknown_direction(self):
@@ -431,7 +431,7 @@ class TestWorkflowsController(base.FunctionalTest):
 
         self.assertEqual(400, resp.status_int)
 
-        self.assertIn("Unknown sort direction", resp.body)
+        self.assertIn("Unknown sort direction", resp.body.decode())
 
     @mock.patch('mistral.db.v2.api.get_workflow_definitions')
     def test_get_all_with_fields_filter(self, mock_get_db_wfs):
@@ -461,7 +461,7 @@ class TestWorkflowsController(base.FunctionalTest):
 
         self.assertIn(
             "nonexist are invalid",
-            resp.body
+            resp.body.decode()
         )
 
     def test_validate(self):