diff --git a/packages/happy-dom/src/event/events/CustomEvent.ts b/packages/happy-dom/src/event/events/CustomEvent.ts
index 86eb8a9c7..2b7dbf41e 100644
--- a/packages/happy-dom/src/event/events/CustomEvent.ts
+++ b/packages/happy-dom/src/event/events/CustomEvent.ts
@@ -17,7 +17,7 @@ export default class CustomEvent extends Event {
 		super(type, eventInit);
 
 		if (eventInit) {
-			this.detail = eventInit.detail || null;
+			this.detail = eventInit.detail != null ? eventInit.detail : null;
 		}
 	}