diff --git a/dev-requirements.txt b/dev-requirements.txt
index 8259c624..27e9b211 100644
--- a/dev-requirements.txt
+++ b/dev-requirements.txt
@@ -2,7 +2,7 @@
 
 blinker==1.4
 coverage==5.2.1
-mock==2.0.0; python_version == "2.7"
+mock==4.0.2; python_version == "2.7"
 pytest==5.4.3; python_version > "2.7"
 pytest<5.0; python_version == "2.7"
 pycodestyle==2.6.0