diff --git a/Related-Projects.md b/Related-Projects.md
index 3c26a5d..33f2054 100644
--- a/Related-Projects.md
+++ b/Related-Projects.md
@@ -15,6 +15,7 @@
 * [mruby-digest](https://github.com/iij/mruby-digest) MD5, RMD160, SHA1, SHA256, SHA384, SHA512 and HMAC Digests by [iij](https://github.com/iij)
 * [mruby-discount](https://github.com/matsumoto-r/mruby-discount) mruby html generater from markdown by [matsumoto_r](https://github.com/matsumoto-r)
 * [mruby-env](https://github.com/iij/mruby-env) ENV class implementation by [iij](https://github.com/iij)
+* [mruby-errno](https://github.com/iij/mruby-errno) Errno module by [iij](https://github.com/iij)
 * [mruby-gntp](https://github.com/mattn/mruby-gntp) Growl Notification Transfer Protocol by [mattn](https://github.com/mattn)
 * [mruby-growthforecast](https://github.com/matsumoto-r/mruby-growthforecast) [GrowthForecast](http://kazeburo.github.com/GrowthForecast/) client using [mruby-httprequest](https://github.com/matsumoto-r/mruby-httprequest) by [matsumoto_r](https://github.com/matsumoto-r)
 * [mruby-http](https://github.com/mattn/mruby-http) Binding for [http-parser](https://github.com/joyent/http-parser) by [mattn](https://github.com/mattn)