Can't set negative value for bigint field with error The integer must be larger or equal to 0

Seems field us hardcoded to be always unsigned?

  public static function defaultStorageSettings() {
    return [
        'unsigned' => TRUE,
        'size' => 'big',
      ] + parent::defaultStorageSettings();
  }

ANd I can't find where to change field type from unsigned to unsigned in Drupal field settings interface.

Simply changing

        'unsigned' => TRUE,

to

        'unsigned' => FALSE,

and recreating field helps solve the problem. Can you expand this setting to Drupal field settings form?

Thanks, patch works well!