diff --git a/4chan_x.user.js b/4chan_x.user.js
index 134a45a15..50624da87 100644
--- a/4chan_x.user.js
+++ b/4chan_x.user.js
@@ -3807,11 +3807,20 @@
       thumb = a.firstChild;
       if (thumb.hidden) {
         rect = a.getBoundingClientRect();
-        if (rect.top < 0) {
-          d.body.scrollTop += rect.top - 42;
-        }
-        if (rect.left < 0) {
-          d.body.scrollLeft += rect.left;
+        if ($.engine === 'webkit') {
+          if (rect.top < 0) {
+            d.body.scrollTop += rect.top - 42;
+          }
+          if (rect.left < 0) {
+            d.body.scrollLeft += rect.left;
+          }
+        } else {
+          if (rect.top < 0) {
+            d.documentElement.scrollTop += rect.top - 42;
+          }
+          if (rect.left < 0) {
+            d.documentElement.scrollLeft += rect.left;
+          }
         }
         return ImageExpand.contract(thumb);
       } else {
diff --git a/script.coffee b/script.coffee
index 3073dedbb..3bfdb6e1c 100644
--- a/script.coffee
+++ b/script.coffee
@@ -2907,8 +2907,12 @@ ImageExpand =
     thumb = a.firstChild
     if thumb.hidden
       rect = a.getBoundingClientRect()
-      d.body.scrollTop += rect.top - 42 if rect.top < 0
-      d.body.scrollLeft += rect.left if rect.left < 0
+      if $.engine is 'webkit'
+        d.body.scrollTop  += rect.top - 42 if rect.top < 0
+        d.body.scrollLeft += rect.left     if rect.left < 0
+      else
+        d.documentElement.scrollTop  += rect.top - 42 if rect.top < 0
+        d.documentElement.scrollLeft += rect.left     if rect.left < 0
       ImageExpand.contract thumb
     else
       ImageExpand.expand thumb