title: Rails 4.0, sass, Zurb Foundation: Warning. Error encountered while saving cache ... can't dump anonymous class
body: <p>After using Bootstrap for a while I wanted to give Zurb Foundation a spin today. I like the grid system and various other elements of Zurb a lot better.</p>
  
  <p>But I noticed refresh times on my (nearly empty) development app were very slow. When I checked the logs I saw dozens of lines like the following:</p>
  
  <pre><code>Warning. Error encountered while saving cache 6552595674261f5b11715c13321f2419e14e57a4/_global.scssc: can't dump anonymous class #&lt;Class:0x0000000562f8e0&gt;
  </code></pre>
  
  <p>They appear any time I make any change to my own (very basic) application.scss file.</p>
  
  <pre><code>@import "foundation_and_overrides";
  
  #container {
    background: #eee;
  }
  </code></pre>
  
  <p>This is the only css I have in the project so far. The (relevant) gems in my project are:</p>
  
  <pre><code>foundation-rails (5.2.0.0)
  sass (3.3.0)
  sass-rails (4.0.1)
  </code></pre>
  
  <p>The sass gems were installed automatically as dependencies by Zurb.</p>
  
  <p>This is all on my local development machine, using thin as a server. No Heroku or anything like that. Tried changing the local cache from file_store to memory_store, just in case, but it makes no difference.</p>
  
  <p>Otherwise it's functioning fine, the css is rendered as expected, it's just painfully slow on each refresh because the cache is failing. Any thoughts would be greatly appreciated.</p>