diff --git a/src/wp-content/themes/twentyfourteen/js/slider.js b/src/wp-content/themes/twentyfourteen/js/slider.js
index 1a08c6263af64..dbe378648606b 100644
--- a/src/wp-content/themes/twentyfourteen/js/slider.js
+++ b/src/wp-content/themes/twentyfourteen/js/slider.js
@@ -213,7 +213,7 @@
 					startY,
 					offset,
 					cwidth,
-					dx,
+					dx = null,
 					startT,
 					scrolling = false,
 					localX = 0,