diff --git a/README.md b/README.md
index 0308a85..eefa908 100644
--- a/README.md
+++ b/README.md
@@ -59,5 +59,6 @@ MIT © [Ivan Nikolić](http://ivannikolic.com)
 
 [ci]: https://travis-ci.com/niksy/postcss-em-media-query
 [ci-img]: https://travis-ci.com/niksy/postcss-em-media-query.svg?branch=master
+[postcss]: https://github.com/postcss/postcss
 
 <!-- prettier-ignore-end -->