diff --git a/docs/requirements.txt b/docs/requirements.txt
index ce91885..4164cd9 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -1,2 +1,3 @@
 -r ../requirements.txt
+mock>=1.3.0,<2.0
 sphinx>=1.3.4,<2.0