diff --git a/date.field.inc b/date.field.inc
index b104702..58807ad 100644
--- a/date.field.inc
+++ b/date.field.inc
@@ -452,6 +452,14 @@ function date_field_widget_settings_form($field, $instance) {
 }
 
 /**
+ * @see _date_field_widget_settings_form_validate().
+ */
+function date_field_widget_settings_form_validate(&$form, &$form_state) {
+  module_load_include('inc', 'date', 'date_admin');
+  return _date_field_widget_settings_form_validate($form, $form_state);
+}
+
+/**
  * Implements hook_field_settings_form().
  */
 function date_field_settings_form($field, $instance, $has_data) {
diff --git a/date_admin.inc b/date_admin.inc
index 993aa09..f3b5168 100644
--- a/date_admin.inc
+++ b/date_admin.inc
@@ -415,7 +415,7 @@ function _date_field_widget_settings_form($field, $instance) {
 /**
  * Form validation handler for _date_field_widget_settings_form().
  */
-function date_field_widget_settings_form_validate(&$form, &$form_state) {
+function _date_field_widget_settings_form_validate(&$form, &$form_state) {
   // The widget settings are in the wrong place in the form because of #tree on
   // the top level.
   $settings = $form_state['values']['instance']['widget']['settings'];