--- a/dom/media/MediaManager.cpp
+++ b/dom/media/MediaManager.cpp
@@ -1660,16 +1660,18 @@ MediaManager::GetUserMedia(
       // the requesting document is not from a host on the whitelist, or
       // we're on Mac OSX 10.6 and WinXP until proved that they work
       if (!Preferences::GetBool(((src == dom::MediaSourceEnum::Browser)?
                                 "media.getusermedia.browser.enabled" :
                                 "media.getusermedia.screensharing.enabled"),
                                 false) ||
 #if defined(XP_MACOSX) || defined(XP_WIN)
           (
+            // Allow tab sharing for all platforms including XP and OSX 10.6
+            (src != dom::MediaSourceEnum::Browser) &&
             !Preferences::GetBool("media.getusermedia.screensharing.allow_on_old_platforms",
                                   false) &&
 #if defined(XP_MACOSX)
             !nsCocoaFeatures::OnLionOrLater()
 #endif
 #if defined (XP_WIN)
             !IsVistaOrLater()
 #endif