Optional requirements fields: requirement, dataType and description

Not providing one of the fields from requirements (in this case "requirement")

    /**
     * Promote user with given role(s)
     *
     * @param Request $request
     * @param $workspaceId
     * @param $userId
     * @ApiDoc(
     *   requirements={
     *      {
     *          "name"="roles",
     *          "dataType"="string|array",
     *          "description"="role name you wish to add."
     *      }
     *  }
     * )
     * @Route(pattern="/workspaces/{workspaceId}/users/{userId}/promote")
     * @return \Symfony\Component\HttpFoundation\Response
     */
    public function postPromoteAction(Request $request, $workspaceId, $userId)
    {
	...

is causing an error

    Key "requirement" for array with keys "dataType, description" does not exist in NelmioApiDocBundle::method.html.twig at line 71