diff --git a/pkgs/applications/networking/browsers/firefox/packages.nix b/pkgs/applications/networking/browsers/firefox/packages.nix
index 63368119ffed..801e1ca0ad40 100644
--- a/pkgs/applications/networking/browsers/firefox/packages.nix
+++ b/pkgs/applications/networking/browsers/firefox/packages.nix
@@ -40,11 +40,11 @@
 
   firefox-beta = buildMozillaMach rec {
     pname = "firefox-beta";
-    version = "121.0b3";
+    version = "121.0b4";
     applicationName = "Mozilla Firefox Beta";
     src = fetchurl {
       url = "mirror://mozilla/firefox/releases/${version}/source/firefox-${version}.source.tar.xz";
-      sha512 = "95dd68c50af5784c44e40ad3a8ac6b4fb259fa8f56bc5e5de940d03dec1838b143712680826b4d260fefdad314464d24679911f21b1095512a86cdf4eb2648c9";
+      sha512 = "b8c1be63be633744b249d2e0ffe77abcc92f0f70c0d7084395031643fb68c0b1fc32a6fcb55a25fc255e4eb8c40e818b209bb0077e416e652ae0c9463045fc12";
     };
 
     meta = {
@@ -69,13 +69,13 @@
 
   firefox-devedition = buildMozillaMach rec {
     pname = "firefox-devedition";
-    version = "121.0b3";
+    version = "121.0b4";
     applicationName = "Mozilla Firefox Developer Edition";
     requireSigning = false;
     branding = "browser/branding/aurora";
     src = fetchurl {
       url = "mirror://mozilla/devedition/releases/${version}/source/firefox-${version}.source.tar.xz";
-      sha512 = "a5ed25159e63122f27bd05810eaf665834022ae407c029734ad41ef1ed5e3956497873f5210b7c385245056718837bd17c47cfc2e2e438a4c3274d2462ce51f8";
+      sha512 = "11234fda39c80a217a715884524e12febf5f920a680b0828d3619ec6ae97fe6e377c36ac86353f1aadb0569e4f04e4105714c29b447eb80ea9bad18bdd664e75";
     };
 
     meta = {