diff --git a/libs/plugins/modifier.date_format.php b/libs/plugins/modifier.date_format.php
index b45b2d4b8..257007480 100644
--- a/libs/plugins/modifier.date_format.php
+++ b/libs/plugins/modifier.date_format.php
@@ -42,9 +42,9 @@ function smarty_modifier_date_format($string, $format = null, $default_date = ''
         }
         $is_loaded = true;
     }
-    if ($string !== '' && $string !== '0000-00-00' && $string !== '0000-00-00 00:00:00') {
+    if (!empty($string) && $string !== '0000-00-00' && $string !== '0000-00-00 00:00:00') {
         $timestamp = smarty_make_timestamp($string);
-    } elseif ($default_date !== '') {
+    } elseif (!empty($default_date)) {
         $timestamp = smarty_make_timestamp($default_date);
     } else {
         return;