diff --git a/browser_patches/firefox/BUILD_NUMBER b/browser_patches/firefox/BUILD_NUMBER
index 56893356b3..0a84548b73 100644
--- a/browser_patches/firefox/BUILD_NUMBER
+++ b/browser_patches/firefox/BUILD_NUMBER
@@ -1,2 +1,2 @@
-1271
-Changed: max@schmitt.mx Thu Jun 10 14:39:06 UTC 2021
+1272
+Changed: max@schmitt.mx Mon Jun 28 10:29:55 UTC 2021
diff --git a/browser_patches/firefox/juggler/NetworkObserver.js b/browser_patches/firefox/juggler/NetworkObserver.js
index 12a3bf355f..ba65a9619b 100644
--- a/browser_patches/firefox/juggler/NetworkObserver.js
+++ b/browser_patches/firefox/juggler/NetworkObserver.js
@@ -589,6 +589,7 @@ class NetworkRequest {
       pageNetwork.emit(PageNetwork.Events.RequestFinished, {
         requestId: this.requestId,
         responseEndTime: this.httpChannel.responseEndTime,
+        transferSize: this.httpChannel.transferSize,
       }, this._frameId);
     }
     this._networkObserver._channelToRequest.delete(this.httpChannel);
diff --git a/browser_patches/firefox/juggler/protocol/Protocol.js b/browser_patches/firefox/juggler/protocol/Protocol.js
index 4f7a514e8b..f658c5082f 100644
--- a/browser_patches/firefox/juggler/protocol/Protocol.js
+++ b/browser_patches/firefox/juggler/protocol/Protocol.js
@@ -488,6 +488,7 @@ const Network = {
     'requestFinished': {
       requestId: t.String,
       responseEndTime: t.Number,
+      transferSize: t.Number,
     },
     'requestFailed': {
       requestId: t.String,