diff --git a/netwerk/protocol/http/src/nsHttpChannel.cpp b/netwerk/protocol/http/src/nsHttpChannel.cpp
index ff3d4427c681..ad5f96ff1366 100644
--- a/netwerk/protocol/http/src/nsHttpChannel.cpp
+++ b/netwerk/protocol/http/src/nsHttpChannel.cpp
@@ -1,3 +1,4 @@
+
 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
 /*
  * The contents of this file are subject to the Mozilla Public
@@ -430,7 +431,9 @@ nsHttpChannel::SetupTransaction()
             mRequestHead.SetHeader(nsHttp::Pragma, "no-cache");
     }
 
-    return mTransaction->SetupRequest(&mRequestHead, mUploadStream, mUploadStreamHasHeaders);
+    return mTransaction->SetupRequest(&mRequestHead, mUploadStream, 
+                                      mUploadStreamHasHeaders, 
+                                      mConnectionInfo->UsingHttpProxy() && !mConnectionInfo->UsingSSL());
 }
 
 void
diff --git a/netwerk/protocol/http/src/nsHttpConnection.cpp b/netwerk/protocol/http/src/nsHttpConnection.cpp
index 4e228eedb6cb..464f162fc97f 100644
--- a/netwerk/protocol/http/src/nsHttpConnection.cpp
+++ b/netwerk/protocol/http/src/nsHttpConnection.cpp
@@ -513,7 +513,7 @@ nsHttpConnection::SetupSSLProxyConnect()
     }
 
     buf.Truncate(0);
-    request.Flatten(buf);
+    request.Flatten(buf, PR_TRUE);
     buf.Append("\r\n");
 
     rv = NS_NewCStringInputStream(getter_AddRefs(mSSLProxyConnectStream), buf);
diff --git a/netwerk/protocol/http/src/nsHttpHeaderArray.cpp b/netwerk/protocol/http/src/nsHttpHeaderArray.cpp
index 044297ebedcb..7383d58ebeca 100644
--- a/netwerk/protocol/http/src/nsHttpHeaderArray.cpp
+++ b/netwerk/protocol/http/src/nsHttpHeaderArray.cpp
@@ -159,11 +159,15 @@ nsHttpHeaderArray::ParseHeaderLine(char *line, nsHttpAtom *hdr, char **val)
 }
 
 void
-nsHttpHeaderArray::Flatten(nsACString &buf)
+nsHttpHeaderArray::Flatten(nsACString &buf, PRBool pruneProxyHeaders)
 {
     PRInt32 i, count = mHeaders.Count();
     for (i=0; i<count; ++i) {
         nsEntry *entry = (nsEntry *) mHeaders[i];
+        // prune proxy headers if requested
+        if (pruneProxyHeaders && ((entry->header == nsHttp::Proxy_Authorization) || 
+                                  (entry->header == nsHttp::Proxy_Connection)))
+            continue;
         buf.Append(entry->header);
         buf.Append(": ");
         buf.Append(entry->value);
diff --git a/netwerk/protocol/http/src/nsHttpHeaderArray.h b/netwerk/protocol/http/src/nsHttpHeaderArray.h
index e3bf5af99dea..5144b369ec09 100644
--- a/netwerk/protocol/http/src/nsHttpHeaderArray.h
+++ b/netwerk/protocol/http/src/nsHttpHeaderArray.h
@@ -47,7 +47,7 @@ public:
     // header value (the substring of the header line -- do not free).
     void ParseHeaderLine(char *line, nsHttpAtom *header=nsnull, char **value=nsnull);
 
-    void Flatten(nsACString &);
+    void Flatten(nsACString &, PRBool pruneProxyHeaders=PR_FALSE);
 
     PRUint32 Count() { return (PRUint32) mHeaders.Count(); }
 
diff --git a/netwerk/protocol/http/src/nsHttpRequestHead.cpp b/netwerk/protocol/http/src/nsHttpRequestHead.cpp
index b9dbbb0b1466..b84c961aa58c 100644
--- a/netwerk/protocol/http/src/nsHttpRequestHead.cpp
+++ b/netwerk/protocol/http/src/nsHttpRequestHead.cpp
@@ -28,7 +28,7 @@
 //-----------------------------------------------------------------------------
 
 void
-nsHttpRequestHead::Flatten(nsACString &buf)
+nsHttpRequestHead::Flatten(nsACString &buf, PRBool pruneProxyHeaders)
 {
     // note: the first append is intentional.
  
@@ -50,5 +50,5 @@ nsHttpRequestHead::Flatten(nsACString &buf)
 
     buf.Append("\r\n");
 
-    mHeaders.Flatten(buf);
+    mHeaders.Flatten(buf, pruneProxyHeaders);
 }
diff --git a/netwerk/protocol/http/src/nsHttpRequestHead.h b/netwerk/protocol/http/src/nsHttpRequestHead.h
index ac9331d15284..cba719bf461c 100644
--- a/netwerk/protocol/http/src/nsHttpRequestHead.h
+++ b/netwerk/protocol/http/src/nsHttpRequestHead.h
@@ -53,7 +53,7 @@ public:
     nsresult GetHeader(nsHttpAtom h, char **v)      { return mHeaders.GetHeader(h, v); }
     void ClearHeaders()                             { mHeaders.Clear(); }
 
-    void Flatten(nsACString &);
+    void Flatten(nsACString &, PRBool pruneProxyHeaders = PR_FALSE);
 
 private:
     nsHttpHeaderArray mHeaders;
diff --git a/netwerk/protocol/http/src/nsHttpResponseHead.cpp b/netwerk/protocol/http/src/nsHttpResponseHead.cpp
index f279a23c7b2e..1ca8378c3e1f 100644
--- a/netwerk/protocol/http/src/nsHttpResponseHead.cpp
+++ b/netwerk/protocol/http/src/nsHttpResponseHead.cpp
@@ -80,7 +80,7 @@ nsHttpResponseHead::Flatten(nsACString &buf, PRBool pruneTransients)
     buf.Append("\r\n");
 
     if (!pruneTransients) {
-        mHeaders.Flatten(buf);
+        mHeaders.Flatten(buf, PR_FALSE);
         return;
     }
 
diff --git a/netwerk/protocol/http/src/nsHttpTransaction.cpp b/netwerk/protocol/http/src/nsHttpTransaction.cpp
index b8b162afa6d4..9d4ba395b005 100644
--- a/netwerk/protocol/http/src/nsHttpTransaction.cpp
+++ b/netwerk/protocol/http/src/nsHttpTransaction.cpp
@@ -119,7 +119,8 @@ nsHttpTransaction::~nsHttpTransaction()
 nsresult
 nsHttpTransaction::SetupRequest(nsHttpRequestHead *requestHead,
                                 nsIInputStream *requestBody,
-                                PRBool requestBodyHasHeaders)
+                                PRBool requestBodyHasHeaders,
+                                PRBool pruneProxyHeaders)
 {
     nsresult rv;
 
@@ -155,7 +156,7 @@ nsHttpTransaction::SetupRequest(nsHttpRequestHead *requestHead,
     mRequestHead = requestHead;
 
     mReqHeaderBuf.SetLength(0);
-    requestHead->Flatten(mReqHeaderBuf);
+    requestHead->Flatten(mReqHeaderBuf, pruneProxyHeaders);
 
 #if defined(PR_LOGGING)
     if (LOG2_ENABLED()) {
diff --git a/netwerk/protocol/http/src/nsHttpTransaction.h b/netwerk/protocol/http/src/nsHttpTransaction.h
index cfb47b237eb0..cb9f148267f0 100644
--- a/netwerk/protocol/http/src/nsHttpTransaction.h
+++ b/netwerk/protocol/http/src/nsHttpTransaction.h
@@ -62,7 +62,8 @@ public:
     // Called to initialize the transaction
     nsresult SetupRequest(nsHttpRequestHead *requestHeaders,
                           nsIInputStream    *requestBody,
-                          PRBool             requestBodyIncludesHeaders);
+                          PRBool             requestBodyIncludesHeaders,
+                          PRBool             pruneProxyHeaders);
 
     nsIStreamListener     *Listener()       { return mListener; }
     nsAHttpConnection     *Connection()     { return mConnection; }