diff --git a/build/monaco/monaco.d.ts.recipe b/build/monaco/monaco.d.ts.recipe
index 71df853a678..ed3a8f5d260 100644
--- a/build/monaco/monaco.d.ts.recipe
+++ b/build/monaco/monaco.d.ts.recipe
@@ -21,7 +21,7 @@ declare namespace monaco {
 	export class Emitter<T> {
 		constructor();
 		readonly event: Event<T>;
-		fire(event?: T): void;
+		fire(event: T): void;
 		dispose(): void;
 	}