diff --git a/Userland/Libraries/LibWeb/HighResolutionTime/DOMHighResTimeStamp.idl b/Userland/Libraries/LibWeb/HighResolutionTime/DOMHighResTimeStamp.idl
new file mode 100644
index 0000000000..7b4c735867
--- /dev/null
+++ b/Userland/Libraries/LibWeb/HighResolutionTime/DOMHighResTimeStamp.idl
@@ -0,0 +1,2 @@
+// https://w3c.github.io/hr-time/#dom-domhighrestimestamp
+typedef double DOMHighResTimeStamp;
diff --git a/Userland/Libraries/LibWeb/HighResolutionTime/Performance.idl b/Userland/Libraries/LibWeb/HighResolutionTime/Performance.idl
index 5ed45278e0..4f2bccf574 100644
--- a/Userland/Libraries/LibWeb/HighResolutionTime/Performance.idl
+++ b/Userland/Libraries/LibWeb/HighResolutionTime/Performance.idl
@@ -1,11 +1,12 @@
 #import <DOM/EventTarget.idl>
+#import <HighResolutionTime/DOMHighResTimeStamp.idl>
 #import <NavigationTiming/PerformanceTiming.idl>
 
 // https://w3c.github.io/hr-time/#sec-performance
 [Exposed=(Window, Worker)]
 interface Performance : EventTarget {
-    double now();
-    readonly attribute double timeOrigin;
+    DOMHighResTimeStamp now();
+    readonly attribute DOMHighResTimeStamp timeOrigin;
 
     readonly attribute PerformanceTiming timing;
 };