diff --git a/requirements.txt b/requirements.txt
index 0dcbc92..a5a1166 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,4 +1,4 @@
-mock==2.0.0; python_version < '3.0'
+mock==5.0.2; python_version < '3.0'
 pyobjc-core==4.1; sys_platform == 'darwin'
 pytest==3.5.0
 pytest-cov==2.5.1