diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 8493daf2de0..0e3eca2ca95 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -7192,7 +7192,7 @@ let
 
   firefoxWrapper = wrapFirefox { browser = pkgs.firefox; };
 
-  firefoxPkgs = pkgs.firefox21Pkgs;
+  firefoxPkgs = pkgs.firefox20Pkgs;
 
   firefox36Pkgs = callPackage ../applications/networking/browsers/firefox/3.6.nix {
     inherit (gnome) libIDL;