diff --git a/pkgs/applications/networking/browsers/firefox/packages/firefox-esr-140.nix b/pkgs/applications/networking/browsers/firefox/packages/firefox-esr-140.nix
index 41606db701de..ac579479844a 100644
--- a/pkgs/applications/networking/browsers/firefox/packages/firefox-esr-140.nix
+++ b/pkgs/applications/networking/browsers/firefox/packages/firefox-esr-140.nix
@@ -1,5 +1,4 @@
 {
-  stdenv,
   lib,
   callPackage,
   fetchurl,
@@ -22,9 +21,6 @@ buildMozillaMach rec {
     homepage = "http://www.mozilla.com/en-US/firefox/";
     maintainers = with lib.maintainers; [ hexa ];
     platforms = lib.platforms.unix;
-    broken = stdenv.buildPlatform.is32bit;
-    # since Firefox 60, build on 32-bit platforms fails with "out of memory".
-    # not in `badPlatforms` because cross-compilation on 64-bit machine might work.
     maxSilent = 14400; # 4h, double the default of 7200s (c.f. #129212, #129115)
     license = lib.licenses.mpl20;
     mainProgram = "firefox";
diff --git a/pkgs/build-support/build-mozilla-mach/default.nix b/pkgs/build-support/build-mozilla-mach/default.nix
index 58f3f6000a56..09eef8b2496f 100644
--- a/pkgs/build-support/build-mozilla-mach/default.nix
+++ b/pkgs/build-support/build-mozilla-mach/default.nix
@@ -145,7 +145,13 @@ in
   ),
   overrideCC,
   buildPackages,
-  pgoSupport ? (stdenv.hostPlatform.isLinux && stdenv.hostPlatform == stdenv.buildPlatform),
+  # PGO merges profile data with a 32-bit llvm-profdata, which runs out of
+  # address space on the huge libxul profile, so disable it on 32-bit.
+  pgoSupport ? (
+    stdenv.hostPlatform.isLinux
+    && stdenv.hostPlatform == stdenv.buildPlatform
+    && stdenv.hostPlatform.is64bit
+  ),
   xvfb-run,
   elfhackSupport ?
     isElfhackPlatform stdenv && !(stdenv.hostPlatform.isMusl && stdenv.hostPlatform.isAarch64),
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 1973ab029799..80118b0bb715 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -8684,7 +8684,6 @@ with pkgs;
     import ../applications/networking/browsers/firefox/packages/firefox-esr-140.nix
       {
         inherit
-          stdenv
           lib
           callPackage
           fetchurl