If your FeatureContext extends MinkContext you can try something like this:
/**
* Override NamedSelector
*/
public function setMinkParameters(array $parameters) {
parent::setMinkParameters ($parameters);
$selectors = $this->getSession()->getSelectorsHandler();
$selectors->getSelector ('named')->registerNamedXpath ('field', <<<XPATH
.//*...
XPATH
);
}
I.e. put your own selector there.