diff --git a/pkgs/applications/networking/browsers/firefox/common.nix b/pkgs/applications/networking/browsers/firefox/common.nix
index b9d95f6d49a9..bcc5ee132bbd 100644
--- a/pkgs/applications/networking/browsers/firefox/common.nix
+++ b/pkgs/applications/networking/browsers/firefox/common.nix
@@ -159,6 +159,8 @@ stdenv.mkDerivation ({
   ++ lib.optional (pname == "firefox-esr" && lib.versionOlder ffversion "69")
     "-Wno-error=format-security");
 
+  MACH_USE_SYSTEM_PYTHON = "1";
+
   postPatch = ''
     rm -rf obj-x86_64-pc-linux-gnu
   '' + lib.optionalString (lib.versionAtLeast ffversion "80") ''
diff --git a/pkgs/applications/networking/browsers/firefox/packages.nix b/pkgs/applications/networking/browsers/firefox/packages.nix
index b05414150666..77c739b1d5b6 100644
--- a/pkgs/applications/networking/browsers/firefox/packages.nix
+++ b/pkgs/applications/networking/browsers/firefox/packages.nix
@@ -7,10 +7,10 @@ in
 rec {
   firefox = common rec {
     pname = "firefox";
-    ffversion = "80.0.1";
+    ffversion = "81.0";
     src = fetchurl {
       url = "mirror://mozilla/firefox/releases/${ffversion}/source/firefox-${ffversion}.source.tar.xz";
-      sha512 = "081sf41r7ickjij3kfrdq29a0d6wz7qv8950kx116kakh8qxgjy8ahk2mfwlcp6digrl4mimi8rl7ns1wjngsmrjh4lvqzh1xglx9cp";
+      sha512 = "1dnxn754vb99mccqrj3wr3pg2scjy42rvs5xc6bw022gh6n8kgipx9pbkapwfivkglynxmmbw1k11ak34zhr1g6p31m3550ad6azq19";
     };
 
     patches = [