diff --git a/src/General/Build.coffee b/src/General/Build.coffee
index 0b76f84e1..1854fd9bd 100755
--- a/src/General/Build.coffee
+++ b/src/General/Build.coffee
@@ -88,11 +88,10 @@ Build =
       .replace(/<[^>]*>/g, '')
     o.info.comment = Build.unescape html
 
-  postFromObject: (data, boardID, suppressThumb) ->
-    o = Build.parseJSON data, boardID
-    Build.post o, suppressThumb
+  postFromObject: (data, boardID) ->
+    Build.post Build.parseJSON data, boardID
 
-  post: (o, suppressThumb) ->
+  post: (o) ->
     {postID, threadID, boardID, file} = o
     {subject, email, name, tripcode, capcode, uniqueID, flagCode, flag, dateUTC, dateText, commentHTML} = o.info
     {staticPath, gifIcon} = Build
@@ -178,7 +177,7 @@ Build =
     root
 
   excerptThread: (board, data, OP) ->
-    nodes = [if OP then OP.nodes.root else Build.postFromObject data, board.ID, true]
+    nodes = [if OP then OP.nodes.root else Build.postFromObject data, board.ID]
     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 74a4dfaab..88b47d7ed 100644
--- a/src/General/Index.coffee
+++ b/src/General/Index.coffee
@@ -650,10 +650,6 @@ 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']
     $.event 'PostsInserted' if doc.contains Index.root
     ThreadHiding.onIndexBuild nodes
diff --git a/src/General/html/Build/File.html b/src/General/html/Build/File.html
index d48f11db2..5d3014a24 100644
--- a/src/General/html/Build/File.html
+++ b/src/General/html/Build/File.html
@@ -15,8 +15,8 @@
       (${file.size}, ${file.dimensions || "PDF"})
     </div>
     <a class="fileThumb?{file.isSpoiler}{ imgspoiler}{}" href="${fileURL}" target="_blank">
-      <img
-        ?{suppressThumb}{ data-src="${fileThumb}"}{ src="${fileThumb}"} 
+      <img 
+        src="${fileThumb}" 
         alt="${file.size}" 
         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 918a4a505..710e35de3 100755
--- a/src/General/lib/clone.class
+++ b/src/General/lib/clone.class
@@ -65,11 +65,6 @@ 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 a6b9b0ee5..d8763b49a 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 or thumb.dataset.src
+      poster:      thumb.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 or thumb.dataset.src)
+    replace = Conf["Replace #{type}"] and !/spoiler/.test thumb.src
     return unless replace or Conf['prefetch']
     return unless [post, post.clones...].some (clone) -> doc.contains clone.nodes.root
     file.isPrefetched = true
@@ -72,8 +72,6 @@ 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 ed159a4ca..4c3e65709 100755
--- a/src/Images/RevealSpoilers.coffee
+++ b/src/Images/RevealSpoilers.coffee
@@ -13,7 +13,4 @@ RevealSpoilers =
     thumb.removeAttribute 'style'
     # Enforce thumbnail size if thumbnail is replaced.
     thumb.style.maxHeight = thumb.style.maxWidth = if @isReply then '125px' else '250px'
-    if thumb.src
-      thumb.src = @file.thumbURL
-    else
-      thumb.dataset.src = @file.thumbURL
+    thumb.src = @file.thumbURL