diff --git a/addons/addon-progress/typings/addon-progress.d.ts b/addons/addon-progress/typings/addon-progress.d.ts
index bcc383a27f..c9431dad22 100644
--- a/addons/addon-progress/typings/addon-progress.d.ts
+++ b/addons/addon-progress/typings/addon-progress.d.ts
@@ -31,7 +31,7 @@ declare module '@xterm/addon-progress' {
     /**
      * An event that fires when the tracked progress changes.
      */
-    public readonly onChange: IEvent<IProgressState> | undefined;
+    public readonly onChange: IEvent<IProgressState>;
 
     /**
      * Gets or sets the current progress tracked by the addon. This can be used