diff --git a/test/helpers.ts b/test/helpers.ts
index 1ea0b19880..dc0cdc693a 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)) {