diff --git a/README.md b/README.md
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--- a/README.md
+++ b/README.md
@@ -2,7 +2,7 @@
 
 A PHP library with a variety of string manipulation functions with multibyte
 support. Offers both OO method chaining and a procedural-style static wrapper.
-Compatible with PHP 5.3+. Inspired by underscore.string.js.
+Tested and compatible with PHP 5.3+ and HHVM. Inspired by underscore.string.js.
 
 [![Build Status](https://travis-ci.org/danielstjules/Stringy.png)](https://travis-ci.org/danielstjules/Stringy)