Field not reflecting the set value

We use module named bxslider and we extended it a bit.

We added a field to the formatter settings using the already existing hooks:
bxslider_field_formatter_info
bxslider_field_formatter_settings_form

I added a checkbox. The checkbox is perfectly visible and i can toggle it but when i save the field settings.
The value i saved in the way i left it when i saved the settings.
But when i open the field settings again the checkbox is unchecked.
Even though i checked it when i last saved it.

Maybe i forgot something in de code for loading it.

here the code in the hooks:

bxslider_field_formatter_settings_form:

<?php
 $element['general']['link_to_node'] = array(
  	'#title' => t('Create link'),
  	'#type' => 'checkbox',
  	'#default_value' => false
  );
?>

bxslider_field_formatter_info:

<?php
 'link_to_node' => FALSE,
?>

API page: https://api.drupal.org/api/drupal/modules%21field_ui%21field_ui.api.php/...

Enter a descriptive title (above) relating to function hook_field_formatter_settings_form, then describe the problem you have found: