diff --git a/mozilla/netwerk/protocol/http/src/nsHttpChannel.cpp b/mozilla/netwerk/protocol/http/src/nsHttpChannel.cpp
index f573c3caaac..c4422a65ad4 100644
--- a/mozilla/netwerk/protocol/http/src/nsHttpChannel.cpp
+++ b/mozilla/netwerk/protocol/http/src/nsHttpChannel.cpp
@@ -173,7 +173,7 @@ nsHttpChannel::Init(nsIURI *uri,
     NS_ADDREF(mConnectionInfo);
 
     // make sure our load flags include this bit if this is a secure channel.
-    if (usingSSL)
+    if (usingSSL && !gHttpHandler->IsPersistentHttpsCachingEnabled()) 
         mLoadFlags |= INHIBIT_PERSISTENT_CACHING;
 
     // Set default request method
@@ -2512,7 +2512,8 @@ nsHttpChannel::SetLoadFlags(nsLoadFlags aLoadFlags)
     mLoadFlags = aLoadFlags;
 
     // don't let anyone overwrite this bit if we're using a secure channel.
-    if (mConnectionInfo && mConnectionInfo->UsingSSL())
+    if (mConnectionInfo && mConnectionInfo->UsingSSL() 
+        && !gHttpHandler->IsPersistentHttpsCachingEnabled())
         mLoadFlags |= INHIBIT_PERSISTENT_CACHING;
 
     return NS_OK;
diff --git a/mozilla/netwerk/protocol/http/src/nsHttpHandler.cpp b/mozilla/netwerk/protocol/http/src/nsHttpHandler.cpp
index f433d1b826e..a8275a0ab47 100644
--- a/mozilla/netwerk/protocol/http/src/nsHttpHandler.cpp
+++ b/mozilla/netwerk/protocol/http/src/nsHttpHandler.cpp
@@ -87,9 +87,11 @@ static NS_DEFINE_CID(kSocketProviderServiceCID, NS_SOCKETPROVIDERSERVICE_CID);
 #define INTL_ACCEPT_LANGUAGES   "intl.accept_languages"
 #define INTL_ACCEPT_CHARSET     "intl.charset.default"
 #define NETWORK_ENABLEIDN       "network.enableIDN"
+#define BROWSER_PREF_PREFIX     "browser.cache."
 
 #define UA_PREF(_pref) UA_PREF_PREFIX _pref
 #define HTTP_PREF(_pref) HTTP_PREF_PREFIX _pref
+#define BROWSER_PREF(_pref) BROWSER_PREF_PREFIX _pref
 
 //-----------------------------------------------------------------------------
 
@@ -143,6 +145,7 @@ nsHttpHandler::nsHttpHandler()
     , mUserAgentIsDirty(PR_TRUE)
     , mUseCache(PR_TRUE)
     , mSendSecureXSiteReferrer(PR_TRUE)
+    , mEnablePersistentHttpsCaching(PR_FALSE)
 {
 #if defined(PR_LOGGING)
     gHttpLog = PR_NewLogModule("nsHttp");
@@ -198,6 +201,7 @@ nsHttpHandler::Init()
             pbi->AddObserver(INTL_ACCEPT_LANGUAGES, this, PR_TRUE); 
             pbi->AddObserver(INTL_ACCEPT_CHARSET, this, PR_TRUE);
             pbi->AddObserver(NETWORK_ENABLEIDN, this, PR_TRUE);
+            pbi->AddObserver(BROWSER_PREF("disk_cache_ssl"), this, PR_TRUE);
         }
         PrefsChanged(prefBranch, nsnull);
     }
@@ -979,6 +983,14 @@ nsHttpHandler::PrefsChanged(nsIPrefBranch *prefs, const char *pref)
         }
     }
 
+    // enable Persistent caching for HTTPS - bug#205921    
+    if (PREF_CHANGED(BROWSER_PREF("disk_cache_ssl"))) {
+        cVar = PR_FALSE;
+        rv = prefs->GetBoolPref(BROWSER_PREF("disk_cache_ssl"), &cVar);
+        if (NS_SUCCEEDED(rv))
+            mEnablePersistentHttpsCaching = cVar;
+    }
+
     //
     // INTL options
     //
diff --git a/mozilla/netwerk/protocol/http/src/nsHttpHandler.h b/mozilla/netwerk/protocol/http/src/nsHttpHandler.h
index a183f18bff5..12f64205631 100644
--- a/mozilla/netwerk/protocol/http/src/nsHttpHandler.h
+++ b/mozilla/netwerk/protocol/http/src/nsHttpHandler.h
@@ -92,6 +92,8 @@ public:
     PRUint16       MaxRequestAttempts()      { return mMaxRequestAttempts; }
     const char    *DefaultSocketType()       { return mDefaultSocketType.get(); /* ok to return null */ }
     nsIIDNService *IDNConverter()            { return mIDNConverter; }
+    
+    PRBool         IsPersistentHttpsCachingEnabled() { return mEnablePersistentHttpsCaching; }
 
     nsHttpAuthCache     *AuthCache() { return &mAuthCache; }
     nsHttpConnectionMgr *ConnMgr()   { return mConnMgr; }
@@ -254,6 +256,9 @@ private:
     // mSendSecureXSiteReferrer: default is false, 
     // if true allow referrer headers between secure non-matching hosts
     PRPackedBool   mSendSecureXSiteReferrer;
+
+    // Persitent HTTPS caching flag
+    PRPackedBool   mEnablePersistentHttpsCaching;
 };
 
 //-----------------------------------------------------------------------------