Trying to start a unicorn daemon as a non-root user but failing hard.

Unicorn gives the the following error:

directory for pid=/var/run/sinatra_test/sinatra_test.pid not writable

So I made the following:

sudo mkdir /var/run/sinatra_test
sudo chown ruby:www-data /var/run/sinatra_test
sudo chmod g+w /var/run/sinatra_test

ls -ld /var/run/sinatra_test returns:

drwxrwxr-x 2 ruby www-data 60 Oct 27 09:55 /var/run/sinatra_test

What am I missing? Still getting Permission denied errors.