set branch on coveralls badge

1 files changed, 1 insertions, 1 deletions

diff --git a/README.md b/README.md
index eadf801..2205fa3 100644
--- a/README.md
+++ b/README.md
@@ -2,7 +2,7 @@
 
 [![Build Status via Travis CI](https://travis-ci.org/caolan/async.svg?branch=master)](https://travis-ci.org/caolan/async)
 [![NPM version](http://img.shields.io/npm/v/async.svg)](https://www.npmjs.org/package/async)
-[![Coverage Status](https://coveralls.io/repos/caolan/async/badge.svg?branch=)](https://coveralls.io/r/caolan/async?branch=)
+[![Coverage Status](https://coveralls.io/repos/caolan/async/badge.svg?branch=master)](https://coveralls.io/r/caolan/async?branch=master)
 
 Async is a utility module which provides straight-forward, powerful functions
 for working with asynchronous JavaScript. Although originally designed for