diff --git a/src/General/Build.coffee b/src/General/Build.coffee
index 0d56e4e97..7bbe30d0e 100755
--- a/src/General/Build.coffee
+++ b/src/General/Build.coffee
@@ -26,7 +26,7 @@ Build =
       "#p#{postID}"
     else
       "/#{boardID}/thread/#{threadID}#p#{postID}"
-  postFromObject: (data, boardID) ->
+  postFromObject: (data, boardID, suppressThumb) ->
     o =
       # id
       postID:   data.no
@@ -70,8 +70,8 @@ Build =
         isSpoiler: !!data.spoiler
         isDeleted: false
         tag:       data.tag
-    Build.post o
-  post: (o) ->
+    Build.post o, suppressThumb
+  post: (o, suppressThumb) ->
     ###
     This function contains code from 4chan-JS (https://github.com/4chan/4chan-JS).
     @license: https://github.com/4chan/4chan-JS/blob/master/LICENSE
@@ -115,6 +115,7 @@ Build =
       shortFilename = Build.shortFilename file.name
       fileSize = $.bytesToString file.size
       fileDims = if file.url[-4..] is '.pdf' then 'PDF' else "#{file.width}x#{file.height}"
+      fileThumb = if file.isSpoiler then Build.spoilerThumb boardID else file.turl
 
     fileBlock = <%= importHTML('Build/File') %>
 
@@ -166,7 +167,7 @@ Build =
     root
 
   excerptThread: (board, data, OP) ->
-    nodes = [if OP then OP.nodes.root else Build.postFromObject data, board.ID]
+    nodes = [if OP then OP.nodes.root else Build.postFromObject data, board.ID, true]
     if data.omitted_posts or !Conf['Show Replies'] and data.replies
       [posts, files] = if Conf['Show Replies']
         # XXX data.omitted_images is not accurate.
diff --git a/src/General/Index.coffee b/src/General/Index.coffee
index d1a8f5073..8302c289c 100644
--- a/src/General/Index.coffee
+++ b/src/General/Index.coffee
@@ -647,6 +647,10 @@ Index =
 
   buildStructure: (nodes) ->
     for node in nodes
+      if thumb = $ 'img[data-src]', node
+        thumb.src = thumb.dataset.src
+        # XXX https://bugzilla.mozilla.org/show_bug.cgi?id=1021289
+        thumb.removeAttribute 'data-src'
       $.add Index.root, [node, $.el 'hr']
     $.event 'PostsInserted' if doc.contains Index.root
     ThreadHiding.onIndexBuild nodes
@@ -661,7 +665,7 @@ Index =
     if Index.search
       Index.searchInput.dataset.searching = 1
     else
-      # XXX https://github.com/greasemonkey/greasemonkey/issues/1571
+      # XXX https://bugzilla.mozilla.org/show_bug.cgi?id=1021289
       Index.searchInput.removeAttribute 'data-searching'
 
   onSearchInput: ->
diff --git a/src/General/html/Build/File.html b/src/General/html/Build/File.html
index f167e6114..2b1e0fed4 100644
--- a/src/General/html/Build/File.html
+++ b/src/General/html/Build/File.html
@@ -18,8 +18,8 @@
       (${fileSize}, ${fileDims})
     </div>
     <a class="fileThumb?{file.isSpoiler}{ imgspoiler}{}" href="${file.url}" target="_blank">
-      <img 
-        src="${file.isSpoiler ? Build.spoilerThumb(boardID) : file.turl}" 
+      <img
+        ?{suppressThumb}{ data-src="${fileThumb}"}{ src="${fileThumb}"} 
         alt="${fileSize}" 
         data-md5="${file.MD5}" 
         style="height: ${file.isSpoiler ? 100 : file.theight}px; width: ${file.isSpoiler ? 100 : file.twidth}px;"
diff --git a/src/General/lib/clone.class b/src/General/lib/clone.class
index 710e35de3..918a4a505 100755
--- a/src/General/lib/clone.class
+++ b/src/General/lib/clone.class
@@ -65,6 +65,11 @@ class Clone extends Post
 
       @file.thumb.muted = true if @file.videoThumb
 
+      if @file.thumb?.dataset.src
+        @file.thumb.src = @file.thumb.dataset.src
+        # XXX https://bugzilla.mozilla.org/show_bug.cgi?id=1021289
+        @file.thumb.removeAttribute 'data-src'
+
       # Contract thumbnails in quote preview
       ImageExpand.contract @ if @file.thumb and contractThumb
 
diff --git a/src/Images/ImageLoader.coffee b/src/Images/ImageLoader.coffee
index 4675362d4..96f243622 100755
--- a/src/Images/ImageLoader.coffee
+++ b/src/Images/ImageLoader.coffee
@@ -38,7 +38,7 @@ ImageLoader =
       preload:     'none'
       loop:        true
       muted:       true
-      poster:      thumb.src
+      poster:      thumb.src or thumb.dataset.src
       textContent: thumb.alt
       className:   thumb.className
     video.setAttribute 'muted', 'muted'
@@ -55,7 +55,7 @@ ImageLoader =
     {isImage, isVideo, thumb, URL} = file
     return if file.isPrefetched or !(isImage or isVideo) or post.isHidden or post.thread.isHidden
     type    = if (match = URL.match(/\.([^.]+)$/)[1].toUpperCase()) is 'JPEG' then 'JPG' else match
-    replace = Conf["Replace #{type}"] and !/spoiler/.test thumb.src
+    replace = Conf["Replace #{type}"] and !/spoiler/.test(thumb.src or thumb.dataset.src)
     return unless replace or Conf['prefetch']
     return unless [post, post.clones...].some (clone) -> doc.contains clone.nodes.root
     file.isPrefetched = true
@@ -72,6 +72,8 @@ ImageLoader =
       $.on el, 'load', ->
         clone.file.thumb.src = URL for clone in post.clones
         thumb.src = URL
+        # XXX https://bugzilla.mozilla.org/show_bug.cgi?id=1021289
+        thumb.removeAttribute 'data-src'
     el.src = URL
 
   toggle: ->
diff --git a/src/Images/RevealSpoilers.coffee b/src/Images/RevealSpoilers.coffee
index 4c3e65709..ed159a4ca 100755
--- a/src/Images/RevealSpoilers.coffee
+++ b/src/Images/RevealSpoilers.coffee
@@ -13,4 +13,7 @@ RevealSpoilers =
     thumb.removeAttribute 'style'
     # Enforce thumbnail size if thumbnail is replaced.
     thumb.style.maxHeight = thumb.style.maxWidth = if @isReply then '125px' else '250px'
-    thumb.src = @file.thumbURL
+    if thumb.src
+      thumb.src = @file.thumbURL
+    else
+      thumb.dataset.src = @file.thumbURL