Adding current employer to a profile generates undefined index error

After adding the field, I get:

Notice: Undefined index: current_employer in CRM_UF_Form_Field->postProcess() (line 666 of /home/jamie/hobo/sites/civicrm/4/sites/all/modules/civicrm/CRM/UF/Form/Field.php).

The line in question is:

$name = $this->_selectFields[$params['field_name'][1]];

The friendly name of the field can easily be derived from params['field_name'][1] but I'm not sure if the absence of current_employer in the $this->_selectFields array is cause for a bigger concern.