 <p>Surprised!</p> <p>Its getting <code>text/plain</code> mime for the CSV, that was the cause of the issue.</p> <p>So to fix this I just found which extension is responsible for <code>text/plain</code> and I found <strong>txt</strong> so i just updated my rules:</p> <pre class="lang-php prettyprint-override"><code>return [ 'sheet' =&gt; 'required|mimes:csv,txt' ]; </code></pre>