diff --git a/tests/python/operator_test.py b/tests/python/operator_test.py
index 69514daf5..a599615d3 100644
--- a/tests/python/operator_test.py
+++ b/tests/python/operator_test.py
@@ -3,7 +3,7 @@
 import pytest
 
 import unittest
-import mock
+from unittest import mock
 
 # Add fixtures to sys.path
 sys.path.append(os.path.join(os.path.dirname(__file__), 'fixtures')) # noqa
diff --git a/tests/python/requirements-dev.txt b/tests/python/requirements-dev.txt
index aa450c967..514fab4c7 100644
--- a/tests/python/requirements-dev.txt
+++ b/tests/python/requirements-dev.txt
@@ -1,5 +1,5 @@
 pytest
-mock
+# dm3_lib = {git = "https://github.com/piraynal/pyDM3reader", tag = "v1.5"}
 diskcache
 h5py
 requests