--- a/netwerk/protocol/http/nsHttpChannel.cpp
+++ b/netwerk/protocol/http/nsHttpChannel.cpp
@@ -735,16 +735,18 @@ nsresult
 nsHttpChannel::ConnectOnTailUnblock()
 {
     nsresult rv;
 
     LOG(("nsHttpChannel::ConnectOnTailUnblock [this=%p]\n", this));
 
     bool isTrackingResource = mIsThirdPartyTrackingResource; // is atomic
     if (isTrackingResource && CheckFastBlocked()) {
+        AntiTrackingCommon::NotifyRejection(this,
+                                            nsIWebProgressListener::STATE_BLOCKED_SLOW_TRACKING_CONTENT);
         Unused << AsyncAbort(NS_ERROR_ABORT);
         CloseCacheEntry(false);
         return NS_OK;
     }
 
     // Consider opening a TCP connection right away.
     SpeculativeConnect();
 

--- a/toolkit/components/antitracking/AntiTrackingCommon.cpp
+++ b/toolkit/components/antitracking/AntiTrackingCommon.cpp
@@ -877,17 +877,18 @@ AntiTrackingCommon::IsOnContentBlockingA
 
 /* static */ void
 AntiTrackingCommon::NotifyRejection(nsIChannel* aChannel,
                                     uint32_t aRejectedReason)
 {
   MOZ_ASSERT(aRejectedReason == nsIWebProgressListener::STATE_COOKIES_BLOCKED_BY_PERMISSION ||
              aRejectedReason == nsIWebProgressListener::STATE_COOKIES_BLOCKED_TRACKER ||
              aRejectedReason == nsIWebProgressListener::STATE_COOKIES_BLOCKED_ALL ||
-             aRejectedReason == nsIWebProgressListener::STATE_COOKIES_BLOCKED_FOREIGN);
+             aRejectedReason == nsIWebProgressListener::STATE_COOKIES_BLOCKED_FOREIGN ||
+             aRejectedReason == nsIWebProgressListener::STATE_BLOCKED_SLOW_TRACKING_CONTENT);
 
   nsCOMPtr<nsIHttpChannel> httpChannel = do_QueryInterface(aChannel);
   if (!httpChannel) {
     return;
   }
 
   // Can be called in EITHER the parent or child process.
   nsCOMPtr<nsIParentChannel> parentChannel;
@@ -920,17 +921,18 @@ AntiTrackingCommon::NotifyRejection(nsIC
 /* static */ void
 AntiTrackingCommon::NotifyRejection(nsPIDOMWindowInner* aWindow,
                                     uint32_t aRejectedReason)
 {
   MOZ_ASSERT(aWindow);
   MOZ_ASSERT(aRejectedReason == nsIWebProgressListener::STATE_COOKIES_BLOCKED_BY_PERMISSION ||
              aRejectedReason == nsIWebProgressListener::STATE_COOKIES_BLOCKED_TRACKER ||
              aRejectedReason == nsIWebProgressListener::STATE_COOKIES_BLOCKED_ALL ||
-             aRejectedReason == nsIWebProgressListener::STATE_COOKIES_BLOCKED_FOREIGN);
+             aRejectedReason == nsIWebProgressListener::STATE_COOKIES_BLOCKED_FOREIGN ||
+             aRejectedReason == nsIWebProgressListener::STATE_BLOCKED_SLOW_TRACKING_CONTENT);
 
   nsIDocument* document = aWindow->GetExtantDoc();
   if (!document) {
     return;
   }
 
   nsCOMPtr<nsIHttpChannel> httpChannel =
     do_QueryInterface(document->GetChannel());

--- a/toolkit/components/antitracking/AntiTrackingCommon.h
+++ b/toolkit/components/antitracking/AntiTrackingCommon.h
@@ -104,16 +104,17 @@ public:
   // The notification is propagated to the child channel if aChannel is a parent
   // channel proxy.
   //
   // aRejectedReason must be one of these values:
   //  * nsIWebProgressListener::STATE_COOKIES_BLOCKED_BY_PERMISSION
   //  * nsIWebProgressListener::STATE_COOKIES_BLOCKED_TRACKER
   //  * nsIWebProgressListener::STATE_COOKIES_BLOCKED_ALL
   //  * nsIWebProgressListener::STATE_COOKIES_BLOCKED_FOREIGN
+  //  * nsIWebProgressListener::STATE_BLOCKED_SLOW_TRACKING_CONTENT
   static void
   NotifyRejection(nsIChannel* aChannel, uint32_t aRejectedReason);
 
   static void
   NotifyRejection(nsPIDOMWindowInner* aWindow, uint32_t aRejectedReason);
 };
 
 } // namespace mozilla

--- a/uriloader/base/nsIWebProgressListener.idl
+++ b/uriloader/base/nsIWebProgressListener.idl
@@ -303,21 +303,25 @@ interface nsIWebProgressListener : nsISu
    *   Rejected because the resource is a tracker and cookie policy doesn't
    *   allow its loading.
    *
    * STATE_COOKIES_BLOCKED_ALL
    *   Rejected because cookie policy blocks all cookies.
    *
    * STATE_COOKIES_BLOCKED_FOREIGN
    *   Rejected because cookie policy blocks 3rd party cookies.
+   *
+   * STATE_BLOCKED_SLOW_TRACKING_CONTENT
+   *   Rejected because of the FastBlock feature.
    */
   const unsigned long STATE_COOKIES_BLOCKED_BY_PERMISSION = 0x10000000;
   const unsigned long STATE_COOKIES_BLOCKED_TRACKER       = 0x20000000;
   const unsigned long STATE_COOKIES_BLOCKED_ALL           = 0x40000000;
   const unsigned long STATE_COOKIES_BLOCKED_FOREIGN       = 0x80000000;
+  const unsigned long STATE_BLOCKED_SLOW_TRACKING_CONTENT = 0x00000040;
 
   /**
    * Notification indicating the state has changed for one of the requests
    * associated with aWebProgress.
    *
    * @param aWebProgress
    *        The nsIWebProgress instance that fired the notification
    * @param aRequest