 <p>Your closing round bracket for options_for_select is at the wrong place. Try:</p> <pre><code>&lt;%= f.select(:reminder, options_for_select([ ['0','0'], ['10','10'], ['25','25'] ]), {}, {:class =&gt; 'form-control'} ) %&gt; </code></pre> <p><a href="http://apidock.com/rails/ActionView/Helpers/FormOptionsHelper/options_for_select" rel="nofollow">options_for_select</a> takes 1 or 2 arguments (2nd argument is optional). Because of the misplaced closing bracket, you are passing 3 arguments to it.</p>