diff --git a/src/runtime/internal/dom.ts b/src/runtime/internal/dom.ts
index 34049b3580f9..0c75665c67e1 100644
--- a/src/runtime/internal/dom.ts
+++ b/src/runtime/internal/dom.ts
@@ -742,9 +742,7 @@ export function toggle_class(element, name, toggle) {
 }
 
 export function custom_event<T = any>(type: string, detail?: T, { bubbles = false, cancelable = false } = {}): CustomEvent<T> {
-	const e: CustomEvent<T> = document.createEvent('CustomEvent');
-	e.initCustomEvent(type, bubbles, cancelable, detail);
-	return e;
+	return new CustomEvent(type, { detail, bubbles, cancelable });
 }
 
 export function query_selector_all(selector: string, parent: HTMLElement = document.body) {
diff --git a/test/helpers.ts b/test/helpers.ts
index 1ea0b198807c..dc0cdc693a35 100644
--- a/test/helpers.ts
+++ b/test/helpers.ts
@@ -61,6 +61,7 @@ global.navigator = window.navigator;
 global.getComputedStyle = window.getComputedStyle;
 global.requestAnimationFrame = null; // placeholder, filled in using set_raf
 global.window = window;
+global.CustomEvent = window.CustomEvent;
 
 // add missing ecmascript globals to window
 for (const key of Object.getOwnPropertyNames(global)) {