undefined $dependentsetting in register_dependency() in base_settings.class.php

public function register_dependency(setting_dependency $dependency) {
    if ($this->is_circular_reference($dependency->get_dependent_setting())) {
        $a = new stdclass();
        $a->alreadydependent = $this->name;
        $a->main = $dependentsetting->get_name();
        throw new base_setting_exception('setting_circular_reference', $a);
    }
    $this->dependencies[$dependency->get_dependent_setting()->get_name()] = $dependency;
    $dependency->get_dependent_setting()->register_dependent_dependency($dependency);
}