diff --git a/src/js/lightbox.js b/src/js/lightbox.js
index e4689f4c..1a70a2f1 100644
--- a/src/js/lightbox.js
+++ b/src/js/lightbox.js
@@ -272,7 +272,7 @@
   // Stretch overlay to fit the viewport
   Lightbox.prototype.sizeOverlay = function() {
     this.$overlay
-      .width($(window).width())
+      .width($(document).width())
       .height($(document).height());
   };