diff --git a/monasca_common/kafka/producer.py b/monasca_common/kafka/producer.py
index 236ced95..e38f79e9 100644
--- a/monasca_common/kafka/producer.py
+++ b/monasca_common/kafka/producer.py
@@ -16,6 +16,8 @@
 import logging
 import time
 
+from six import PY2
+
 import monasca_common.kafka_lib.client as kafka_client
 import monasca_common.kafka_lib.producer as kafka_producer
 
@@ -53,7 +55,8 @@ class KafkaProducer(object):
             try:
                 if key is None:
                     key = int(time.time() * 1000)
-                self._producer.send_messages(topic, str(key), *messages)
+                key = str(key) if PY2 else bytes(str(key), 'utf-8')
+                self._producer.send_messages(topic, key, *messages)
                 success = True
             except Exception:
                 if first:
diff --git a/monasca_common/tests/test_kafka.py b/monasca_common/tests/test_kafka.py
index 5f7443b8..f28ec139 100644
--- a/monasca_common/tests/test_kafka.py
+++ b/monasca_common/tests/test_kafka.py
@@ -51,19 +51,20 @@ class TestKafkaProducer(base.BaseTestCase):
     def test_kafka_producer_publish(self):
         topic = FAKE_KAFKA_TOPIC
         messages = ['message']
-        key = 'key'
+        key = "key"
+        expected_key = b"key"
 
         self.monasca_kafka_producer.publish(topic, messages, key)
 
         self.producer.send_messages.assert_called_once_with(
-            topic, key, *messages)
+            topic, expected_key, *messages)
 
     @mock.patch('monasca_common.kafka.producer.time')
     def test_kafka_producer_publish_one_message_without_key(self, mock_time):
         topic = FAKE_KAFKA_TOPIC
         message = 'not_a_list'
         mock_time.time.return_value = 1
-        expected_key = '1000'
+        expected_key = b'1000'
 
         self.monasca_kafka_producer.publish(topic, message)