diff --git a/4chan_x.js b/4chan_x.js
index 2ca70e92c..51e046db4 100644
--- a/4chan_x.js
+++ b/4chan_x.js
@@ -2237,12 +2237,17 @@
       return $.rm(thumb.nextSibling);
     },
     expand: function(thumb) {
-      var a, img;
+      var a, filesize, img, max, _, _ref2;
       $.hide(thumb);
       a = thumb.parentNode;
       img = $.el('img', {
         src: a.href
       });
+      if (a.parentNode.className !== 'op') {
+        filesize = $.x('preceding::span[@class="filesize"][1]', a);
+        _ref2 = filesize.textContent.match(/(\d+)x/), _ = _ref2[0], max = _ref2[1];
+        img.setAttribute('style', "max-width: -moz-calc(" + max + "px);");
+      }
       return a.appendChild(img);
     },
     dialog: function() {
diff --git a/script.coffee b/script.coffee
index 02d218ec7..bbfbc7a5f 100644
--- a/script.coffee
+++ b/script.coffee
@@ -1716,6 +1716,10 @@ imgExpand =
     a = thumb.parentNode
     img = $.el 'img',
       src: a.href
+    unless a.parentNode.className is 'op'
+      filesize = $.x 'preceding::span[@class="filesize"][1]', a
+      [_, max] = filesize.textContent.match /(\d+)x/
+      img.setAttribute 'style', "max-width: -moz-calc(#{max}px);"
     a.appendChild img
 
   dialog: ->