 <p>I got the error in ermenkoff's solution.</p> <p><strong>Error</strong>: AbsoluteAssetPathError</p> <p>It was fixed by <strong>removing</strong> "/assets/" from the url.</p> <pre><code>:default_url =&gt; ":style/missing_avatar.jpg" </code></pre> <p>Images are stored in:</p> <pre><code>app/assets/images/medium/missing_avatar.jpg app/assets/images/thumbs/missing_avatar.jpg </code></pre>