diff --git a/date_popup/date_popup.module b/date_popup/date_popup.module
index e91cc8a..b0eb25a 100644
--- a/date_popup/date_popup.module
+++ b/date_popup/date_popup.module
@@ -474,10 +474,11 @@ function date_popup_process_time_part(&$element) {
       $grans = array('hour', 'minute', 'second');
       $time_granularity = array_intersect($granularity, $grans);
       $format = date_popup_format_to_popup_time(date_limit_format($element['#date_format'], $time_granularity), 'wvega');
+      $default_value = isset($element['#default_value']) ? $element['#default_value'] : '';
       // The first value in the dropdown list should be the same as the element
       // default_value, but it needs to be in JS format (i.e. milliseconds since
       // the epoch).
-      $start_time = new DateObject($element['#default_value'], $element['#date_timezone'], DATE_FORMAT_DATETIME);
+      $start_time = new DateObject($default_value, $element['#date_timezone'], DATE_FORMAT_DATETIME);
       date_increment_round($start_time, $element['#date_increment']);
       $start_time = $start_time->format(DATE_FORMAT_UNIX) * 1000;
       $settings = array(