diff --git a/src/General/lib/post.class b/src/General/lib/post.class
index 6ca9229a1..2cce8bb31 100755
--- a/src/General/lib/post.class
+++ b/src/General/lib/post.class
@@ -183,7 +183,7 @@ class Post
     if (thumb = $ '.fileThumb > [data-md5]', fileEl)
       $.extend @file,
         thumb:     thumb
-        thumbURL:  "#{location.protocol}//i.4cdn.org/#{@board}/#{link.href.match(/(\d+)\./)[1]}s.jpg"
+        thumbURL:  if m = link.href.match(/\d+(?=\.\w+$)/) then "#{location.protocol}//i.4cdn.org/#{@board}/#{m[0]}s.jpg"
         MD5:       thumb.dataset.md5
         isSpoiler: $.hasClass thumb.parentNode, 'imgspoiler'