diff --git a/lib/utils/gestures.html b/lib/utils/gestures.html
index 85677dad4d..7ccc4ad6d8 100644
--- a/lib/utils/gestures.html
+++ b/lib/utils/gestures.html
@@ -913,14 +913,14 @@
     },
     /**
      * @this {GestureRecognizer}
-     * @param {Event} e
-     * @param {Function} preventer
+     * @param {Event | Touch} e
+     * @param {Event=} preventer
      */
     forward: function(e, preventer) {
       let dx = Math.abs(e.clientX - this.info.x);
       let dy = Math.abs(e.clientY - this.info.y);
       // find original target from `preventer` for TouchEvents, or `e` for MouseEvents
-      let t = Gestures._findOriginalTarget(preventer || e);
+      let t = Gestures._findOriginalTarget(/** @type {Event} */(preventer || e));
       // dx,dy can be NaN if `click` has been simulated and there was no `down` for `start`
       if (isNaN(dx) || isNaN(dy) || (dx <= TAP_DISTANCE && dy <= TAP_DISTANCE) || isSyntheticClick(e)) {
         // prevent taps from being generated if an event has canceled them