 <p>Is <code>@networks_domentic</code> getting set properly in the controller? Add <code>&lt;%= @networks_domestic.inspect %&gt;</code> right before line 52 and see what you get. Check for <code>@networkd_domestic.nil?</code> in the controller and make sure you don't send <code>nil</code> to the view.</p> <p>EDIT:</p> <p>If you look at the source for <a href="http://api.rubyonrails.org/classes/ActionView/Helpers/FormOptionsHelper.html#M001628" rel="nofollow noreferrer"><code>options_from_collection_for_select</code></a> you will see that it is calling <code>map</code> on the collection you pass (@networks_domestic in this case).</p>