diff --git a/requirements_dev.txt b/requirements_dev.txt
index 9ebbf42..0d4dd50 100644
--- a/requirements_dev.txt
+++ b/requirements_dev.txt
@@ -7,7 +7,7 @@ watchdog>=0.8.3
 flake8>=2.6.0
 tox>=2.3.1
 coverage>=4.1
-mock==4.0.2
+mock==5.1.0
 PyYAML>=3.11
 pytest>=4.3.1
 pytest-cov==2.8.1