diff --git a/requirements_dev.txt b/requirements_dev.txt
index d51db62..b5b2aa7 100644
--- a/requirements_dev.txt
+++ b/requirements_dev.txt
@@ -6,5 +6,5 @@ pep8==1.5.7 # flake8
 pyflakes==2.1.1 # flake8
 flake8==2.4.1
 
-mock==1.0.1
+mock==4.0.3
 nose==1.3.7
\ No newline at end of file