Make multiple select dropdown required w/ verification

I'm trying to create a multiple dropdown in a form w/ verification. I got the verification to work on inputs and dropdowns where it wasn't multi select but when I added the multiple option then it doesn't accept that items have been selected.

For example, this works.

<input required="true" type="text" class="form-control required" id="C___of_Employees1" name="C___of_Employees1" placeholder="Number of Employees*" value="" >

But this dropdown doesn't think anything is selected...

<select required="true" multiple class="form-control selectpicker" data-style="btn btn-link" id="businessmarkets" name="businessmarkets" >
  <option value="" disables selected="false" style="display: none;" id="businessmarkets">Business Markets Served*</option>
  <option value="Large Enterprise (10,000 Employees)">Large Enterprise (10,000 Employees)</option>
  <option value="Enterprise (1,000-10,000 Employees)">Enterprise (1,000-10,000 Employees)</option>
  <option value="Small / Medium (1-1,000 Employees)">Small / Medium (1-1,000 Employees)</option>
</select>