diff --git a/src/pvv/side/event.php b/src/pvv/side/event.php
index 4f56828..d8024c1 100644
--- a/src/pvv/side/event.php
+++ b/src/pvv/side/event.php
@@ -2,6 +2,7 @@
 namespace pvv\side;
 
 use \DateTimeImmutable;
+use \DateInterval;
 
 abstract class Event {