diff --git a/pkgs/applications/networking/browsers/firefox/15.0.nix b/pkgs/applications/networking/browsers/firefox/15.0.nix
index c0b45d45cf3..cb79f4422eb 100644
--- a/pkgs/applications/networking/browsers/firefox/15.0.nix
+++ b/pkgs/applications/networking/browsers/firefox/15.0.nix
@@ -21,7 +21,7 @@ rec {
 
 
   src = fetchurl {
-    url = "http://releases.mozilla.org/pub/mozilla.org/firefox/releases/${firefoxVersion}/source/firefox-${firefoxVersion}.source.tar.bz2";
+    url = "ftp://ftp.mozilla.org/pub/mozilla.org/firefox/releases/${firefoxVersion}/source/firefox-${firefoxVersion}.source.tar.bz2";
     sha1 = "bdbc4b6656c59b926e18f99b3335484427d08641";
   };
 
diff --git a/pkgs/applications/networking/mailreaders/thunderbird/11.x.nix b/pkgs/applications/networking/mailreaders/thunderbird/11.x.nix
index 0c8ba4b05ff..0d36bf88739 100644
--- a/pkgs/applications/networking/mailreaders/thunderbird/11.x.nix
+++ b/pkgs/applications/networking/mailreaders/thunderbird/11.x.nix
@@ -26,7 +26,7 @@ stdenv.mkDerivation {
   name = "thunderbird-${version}";
 
   src = fetchurl {
-    url = "http://releases.mozilla.org/pub/mozilla.org/thunderbird/releases/${version}/source/thunderbird-${version}.source.tar.bz2";
+    url = "ftp://ftp.mozilla.org/pub/thunderbird/releases/11.0.1/source/thunderbird-${version}.source.tar.bz2";
     sha1 = "037344b451b1c031472d92f96d401b15d8e3e7d3";
   };