title: Ruby On Rails, Redis::CommandError: ERR wrong number of arguments for 'set' command
body: <p>Why does this code</p>
  
  <pre><code>redis.set("test", true, ex: 24.hours)
  </code></pre>
  
  <p>return the following exception?</p>
  
  <pre><code>Redis::CommandError: ERR wrong number of arguments for 'set' command
  </code></pre>
  
  <p>I use these gems</p>
  
  <ul>
  <li>redis (3.2.0)</li>
  <li>redis-rails (4.0.0)</li>
  </ul>