diff --git a/README.md b/README.md
index b6b5b47..6757cf3 100644
--- a/README.md
+++ b/README.md
@@ -74,6 +74,10 @@ cd grass
 cargo b --release
 ./sass-spec/sass-spec.rb -c './target/release/grass'
 ```
+Note: you will have to install [ruby](https://www.ruby-lang.org/en/downloads/),
+[bundler](https://bundler.io/) and run `bundle install` in `./sass-spec/`.
+This might also require you to install the requirements separately
+for [curses](https://github.com/ruby/curses).
 
 These numbers come from a default run of the Sass specification as shown above.