form_set_error highlight offending field? form_set_error supposedly takes the name of the offending form element as the first param.

I have a form element that is named "field_reviewer_terms_of_service[value]" (as taken from firebug). My code that sets the error is:

    form_set_error('field_reviewer_terms_of_service[value]', t('You must agree to the Terms of Service.'));


The error shows up in the messages, but doesn't highlight the form element itself. What am I doing wrong?

Edited with HTML of form element:

&lt;div id="edit-field-applicant-terms-of-service-value-wrapper" class="form-item"&gt;
 &lt;label for="edit-field-applicant-terms-of-service-value" class="option"&gt;&lt;input type="checkbox" class="form-checkbox required error" value="1" id="edit-field-applicant-terms-of-service-value" name="field_applicant_terms_of_service[value]"&gt; I agree to the &lt;a href="/terms_of_service" target="_blank"&gt;Terms of Service&lt;/a&gt;&lt;/label&gt;
&lt;/div&gt;
Don't put the [value] inside, it should work with only 

form_set_error('field_reviewer_terms_of_service', t('You must agree to the Terms of Service.'));


See the documentation for form_set_error().
You may have to use some [value inside your field if it is multivalued, see this comment but we need to see the HTML ouput for your field.