diff --git a/pkgs/applications/networking/browsers/firefox/packages.nix b/pkgs/applications/networking/browsers/firefox/packages.nix
index 17c581882b8a..e34120de9c00 100644
--- a/pkgs/applications/networking/browsers/firefox/packages.nix
+++ b/pkgs/applications/networking/browsers/firefox/packages.nix
@@ -32,10 +32,10 @@ rec {
 
   firefox-esr-91 = common rec {
     pname = "firefox-esr";
-    version = "91.8.0esr";
+    version = "91.9.0esr";
     src = fetchurl {
       url = "mirror://mozilla/firefox/releases/${version}/source/firefox-${version}.source.tar.xz";
-      sha512 = "edea2c7d4d3d0322091b20b623019ef041090d9f89f33c8e3140f66a54624261f278257393db70d2038154de8ee02da0bee6ecf85c281f3558338da71fc173c3";
+      sha512 = "fd69d489429052013d2c1b8b766a47920ecee62f0688505758f593b27ae66d6343b9107163749406251aedebdf836147e4d562415a811b04d7ab2ae31e32f133";
     };
 
     meta = {