diff --git a/htdocs/core/lib/functions.lib.php b/htdocs/core/lib/functions.lib.php
index e238b1e5834..d679882161f 100644
--- a/htdocs/core/lib/functions.lib.php
+++ b/htdocs/core/lib/functions.lib.php
@@ -1053,7 +1053,11 @@ function dol_mktime($hour,$minute,$second,$month,$day,$year,$gm=false,$check=1)
 				$default_timezone=@date_default_timezone_get();
 			}
 		}
-		else $localtz = new DateTimeZone('UTC');
+		
+		if (empty($localtz)) {
+			$localtz = new DateTimeZone('UTC');
+		}
+		
 		$dt = new DateTime(null,$localtz);
 		$dt->setDate($year,$month,$day);
 		$dt->setTime((int) $hour, (int) $minute, (int) $second);