diff --git a/README.rst b/README.rst
index 21bd63fd642bcc15fd32663ec2d22aec784f942d..5ffcff22cda1db82f63a6ede54eec87dceb2ef16 100644
--- a/README.rst
+++ b/README.rst
@@ -120,6 +120,7 @@ Installing prerequisites on Mac OS X::
     xcode-select --install
     sudo easy_install pip
     sudo pip install virtualenv
+    brew install pkg-config libffi
 
 Installing prerequisites on Raspbian::