diff --git a/doc/00-intro.md b/doc/00-intro.md
index ea0ea63b0..f86ee400f 100644
--- a/doc/00-intro.md
+++ b/doc/00-intro.md
@@ -113,6 +113,7 @@ Composer is part of the homebrew-php project.
 ```sh
 brew update
 brew tap homebrew/homebrew-php
+brew tap homebrew/dupes
 brew tap homebrew/versions
 brew install php55-intl
 brew install homebrew/php/composer