 <p><code>config.assets.initialize_on_precompile = false</code></p> <p>Include that in application.rb, ABOVE module APPNAME</p> <p>I had originally included it inside </p> <blockquote> <p>class Application &lt; Rails::Application</p> </blockquote> <p>Edit: actually, the above didn't fix it.</p> <p>I had to do this</p> <p><a href="https://devcenter.heroku.com/articles/labs-user-env-compile">https://devcenter.heroku.com/articles/labs-user-env-compile</a></p>