diff --git a/pkgs/applications/networking/browsers/firefox/default.nix b/pkgs/applications/networking/browsers/firefox/default.nix
index 2c433d12db55..ff206c50f34a 100644
--- a/pkgs/applications/networking/browsers/firefox/default.nix
+++ b/pkgs/applications/networking/browsers/firefox/default.nix
@@ -16,14 +16,14 @@
 
 assert stdenv.cc ? libc && stdenv.cc.libc != null;
 
-let version = "40.0.2"; in
+let version = "40.0.3"; in
 
 stdenv.mkDerivation rec {
   name = "firefox-${version}";
 
   src = fetchurl {
     url = "http://ftp.mozilla.org/pub/mozilla.org/firefox/releases/${version}/source/firefox-${version}.source.tar.bz2";
-    sha1 = "b5d79fa3684284bfeb7277e99c756b8688e8121d";
+    sha1 = "6ddda46bd6540ab3ae932fbb5ffec8e9a85cab13";
   };
 
   buildInputs =