diff --git a/test/runner/requirements/constraints.txt b/test/runner/requirements/constraints.txt
index e3c5623bcd..7b739fa0f7 100644
--- a/test/runner/requirements/constraints.txt
+++ b/test/runner/requirements/constraints.txt
@@ -21,6 +21,8 @@ virtualenv < 16.0.0 ; python_version < '2.7' # virtualenv 16.0.0 and later requi
 pyopenssl < 18.0.0 ; python_version < '2.7' # pyOpenSSL 18.0.0 and later require python 2.7 or later
 pyfmg == 0.6.1 # newer versions do not pass current unit tests
 pycparser < 2.19 ; python_version < '2.7' # pycparser 2.19 and later require python 2.7 or later
+mock >= 2.0.0 # needed for features backported from Python 3.6 unittest.mock (assert_called, assert_called_once...)
+pytest-mock >= 1.4.0 # needed for mock_use_standalone_module pytest option
 
 # freeze pylint and its requirements for consistent test results
 astroid == 2.0.4
diff --git a/tox.ini b/tox.ini
index 33522366c3..8a5c8ddb3b 100644
--- a/tox.ini
+++ b/tox.ini
@@ -22,6 +22,7 @@ passenv =
 [pytest]
 xfail_strict = true
 cache_dir = .pytest_cache
+mock_use_standalone_module = true
 
 [flake8]
 # These are things that the devs don't agree make the code more readable