diff --git a/browser_patches/firefox/BUILD_NUMBER b/browser_patches/firefox/BUILD_NUMBER
index 29e8053650..4bdcbffe9e 100644
--- a/browser_patches/firefox/BUILD_NUMBER
+++ b/browser_patches/firefox/BUILD_NUMBER
@@ -1,2 +1,2 @@
-1205
-Changed: dgozman@gmail.com Sun Nov  8 07:09:21 PST 2020
+1206
+Changed: yurys@chromium.org Thu 12 Nov 2020 10:23:24 AM PST
diff --git a/browser_patches/firefox/juggler/NetworkObserver.js b/browser_patches/firefox/juggler/NetworkObserver.js
index df7dedfe4c..274e117ebe 100644
--- a/browser_patches/firefox/juggler/NetworkObserver.js
+++ b/browser_patches/firefox/juggler/NetworkObserver.js
@@ -238,9 +238,20 @@ class NetworkRequest {
       const synthesized = Cc["@mozilla.org/io/string-input-stream;1"].createInstance(Ci.nsIStringInputStream);
       const body = atob(postData);
       synthesized.setData(body, body.length);
+
+      const overridenHeader = (lowerCaseName, defaultValue) => {
+        if (headers) {
+          for (const header of headers) {
+            if (header.name.toLowerCase() === lowerCaseName) {
+              return header.value;
+            }
+          }
+        }
+        return defaultValue;
+      }
       // Clear content-length, so that upload stream resets it.
-      this.httpChannel.setRequestHeader('content-length', '', false /* merge */);
-      this.httpChannel.explicitSetUploadStream(synthesized, 'application/octet-stream', -1, this.httpChannel.requestMethod, false);
+      this.httpChannel.setRequestHeader('content-length', overridenHeader('content-length', ''), false /* merge */);
+      this.httpChannel.explicitSetUploadStream(synthesized, overridenHeader('content-type', 'application/octet-stream'), -1, this.httpChannel.requestMethod, false);
     }
   }