diff --git a/date_popup/date_popup.module b/date_popup/date_popup.module
index ca292ef..98d00b1 100644
--- a/date_popup/date_popup.module
+++ b/date_popup/date_popup.module
@@ -559,7 +559,12 @@ function date_popup_time_formats($with_seconds = FALSE) {
  * TODO Remove any formats not supported by the widget, if any.
  */
 function date_popup_formats() {
-  $formats = str_replace('i', 'i:s', array_keys(system_get_date_formats('short')));
+  $date_formats = system_get_date_formats('short');
+  $custom_formats = system_get_date_formats('custom');
+  if (is_array($custom_formats)) {
+    $date_formats = array_merge($date_formats, $custom_formats);
+  }
+  $formats = str_replace('i', 'i:s', array_keys($date_formats));
   $formats = drupal_map_assoc($formats);
   return $formats;
 }