diff --git a/js/ui/keyboard.js b/js/ui/keyboard.js
index 7ce866802..4af2b18c4 100644
--- a/js/ui/keyboard.js
+++ b/js/ui/keyboard.js
@@ -722,7 +722,7 @@ var EmojiPager = GObject.registerClass({
 
     _onPan(action) {
         let [dist_, dx, dy_] = action.get_motion_delta(0);
-        this.delta = this.delta + dx;
+        this.delta += dx;
 
         if (this._currentKey != null) {
             this._currentKey.cancel();