diff --git a/Userland/Libraries/LibWeb/HighResolutionTime/Performance.idl b/Userland/Libraries/LibWeb/HighResolutionTime/Performance.idl
index c269172f315..bd92ebc2cb2 100644
--- a/Userland/Libraries/LibWeb/HighResolutionTime/Performance.idl
+++ b/Userland/Libraries/LibWeb/HighResolutionTime/Performance.idl
@@ -13,6 +13,7 @@ typedef sequence<PerformanceEntry> PerformanceEntryList;
 interface Performance : EventTarget {
     DOMHighResTimeStamp now();
     readonly attribute DOMHighResTimeStamp timeOrigin;
+    [Default] object toJSON();
 
     readonly attribute PerformanceTiming timing;