diff --git a/README.md b/README.md
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@@ -3,6 +3,8 @@ R3
 
 [![Build Status](https://travis-ci.org/c9s/r3.svg?branch=master)](https://travis-ci.org/c9s/r3)
 
+[![Coverage Status](https://coveralls.io/repos/c9s/r3/badge.png)](https://coveralls.io/r/c9s/r3)
+
 R3 is an URL router library with high performance, thus, it's implemented in C.
 It compiles your route paths into a prefix trie.