diff --git a/monasca/common/messaging/publisher.py b/monasca/common/messaging/publisher.py
index ea84043..324d075 100644
--- a/monasca/common/messaging/publisher.py
+++ b/monasca/common/messaging/publisher.py
@@ -13,10 +13,11 @@
 # under the License.
 
 import abc
+import six
 
 
+@six.add_metaclass(abc.ABCMeta)
 class Publisher(object):
-    __metaclass__ = abc.ABCMeta
 
     @abc.abstractmethod
     def send_message(self, message):
diff --git a/monasca/common/repositories/events_repository.py b/monasca/common/repositories/events_repository.py
index 1dd9d0a..7880c4f 100644
--- a/monasca/common/repositories/events_repository.py
+++ b/monasca/common/repositories/events_repository.py
@@ -13,10 +13,11 @@
 # under the License.
 
 import abc
+import six
 
 
+@six.add_metaclass(abc.ABCMeta)
 class EventsRepository(object):
-    __metaclass__ = abc.ABCMeta
 
     @abc.abstractmethod
     def list_events(self, tenant_id, name, dimensions):
diff --git a/monasca/common/repositories/metrics_repository.py b/monasca/common/repositories/metrics_repository.py
index a4d8d03..cb25b15 100644
--- a/monasca/common/repositories/metrics_repository.py
+++ b/monasca/common/repositories/metrics_repository.py
@@ -13,10 +13,11 @@
 # under the License.
 
 import abc
+import six
 
 
+@six.add_metaclass(abc.ABCMeta)
 class MetricsRepository(object):
-    __metaclass__ = abc.ABCMeta
 
     @abc.abstractmethod
     def list_metrics(self, tenant_id, name, dimensions):
diff --git a/monasca/common/repositories/transforms_repository.py b/monasca/common/repositories/transforms_repository.py
index 82377b1..e921356 100644
--- a/monasca/common/repositories/transforms_repository.py
+++ b/monasca/common/repositories/transforms_repository.py
@@ -13,10 +13,11 @@
 # under the License.
 
 import abc
+import six
 
 
+@six.add_metaclass(abc.ABCMeta)
 class TransformsRepository(object):
-    __metaclass__ = abc.ABCMeta
 
     @abc.abstractmethod
     def create_transforms(self, id, tenant_id, name, description, specification, enabled):