diff --git a/lower-constraints.txt b/lower-constraints.txt
index 7627ef7..60cc639 100644
--- a/lower-constraints.txt
+++ b/lower-constraints.txt
@@ -22,7 +22,6 @@ kazoo==2.2
 keystoneauth1==3.4.0
 linecache2==1.0.0
 mccabe==0.2.1
-mock==2.0.0
 monasca-common==2.16.0
 monasca-statsd==1.4.0
 monotonic==0.6
diff --git a/tests/test_utils.py b/tests/test_utils.py
index a98b3aa..0222fc1 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -12,7 +12,7 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
-from mock import patch
+from unittest.mock import patch
 
 from monasca_notification.common import utils
 from tests import base