diff --git a/nixos/modules/system/activation/activatable-system.nix b/nixos/modules/system/activation/activatable-system.nix
index 69014331c2a0..656049053f15 100644
--- a/nixos/modules/system/activation/activatable-system.nix
+++ b/nixos/modules/system/activation/activatable-system.nix
@@ -19,6 +19,7 @@ in
     system.systemBuilderArgs = {
       activationScript = config.system.activationScripts.script;
       dryActivationScript = config.system.dryActivationScript;
+      installBootLoader = config.system.build.installBootLoader;
       localeArchive = "${config.i18n.glibcLocales}/lib/locale/locale-archive";
       distroId = config.system.nixos.distroId;
       perl = pkgs.perl.withPackages (p: with p; [ ConfigIniFiles FileSlurp ]);
diff --git a/nixos/modules/system/activation/activation-script.nix b/nixos/modules/system/activation/activation-script.nix
index f23d4809e356..c8407dd6779a 100644
--- a/nixos/modules/system/activation/activation-script.nix
+++ b/nixos/modules/system/activation/activation-script.nix
@@ -204,6 +204,27 @@ in
         `/usr/bin/env`.
       '';
     };
+
+    system.build.installBootLoader = mkOption {
+      internal = true;
+      # "; true" => make the `$out` argument from switch-to-configuration.pl
+      #             go to `true` instead of `echo`, hiding the useless path
+      #             from the log.
+      default = "echo 'Warning: do not know how to make this configuration bootable; please enable a boot loader.' 1>&2; true";
+      description = lib.mdDoc ''
+        A program that writes a bootloader installation script to the path passed in the first command line argument.
+
+        See `nixos/modules/system/activation/switch-to-configuration.pl`.
+      '';
+      type = types.unique {
+        message = ''
+          Only one bootloader can be enabled at a time. This requirement has not
+          been checked until NixOS 22.05. Earlier versions defaulted to the last
+          definition. Change your configuration to enable only one bootloader.
+        '';
+      } (types.either types.str types.package);
+    };
+
   };
 
 
diff --git a/nixos/modules/system/activation/top-level.nix b/nixos/modules/system/activation/top-level.nix
index 4973d61da13e..22bc6e6b92a3 100644
--- a/nixos/modules/system/activation/top-level.nix
+++ b/nixos/modules/system/activation/top-level.nix
@@ -88,7 +88,6 @@ let
     utillinux = pkgs.util-linux;
 
     kernelParams = config.boot.kernelParams;
-    installBootLoader = config.system.build.installBootLoader;
     nixosLabel = config.system.nixos.label;
 
     inherit (config.system) extraDependencies;
@@ -153,26 +152,6 @@ in
     };
 
     system.build = {
-      installBootLoader = mkOption {
-        internal = true;
-        # "; true" => make the `$out` argument from switch-to-configuration.pl
-        #             go to `true` instead of `echo`, hiding the useless path
-        #             from the log.
-        default = "echo 'Warning: do not know how to make this configuration bootable; please enable a boot loader.' 1>&2; true";
-        description = lib.mdDoc ''
-          A program that writes a bootloader installation script to the path passed in the first command line argument.
-
-          See `nixos/modules/system/activation/switch-to-configuration.pl`.
-        '';
-        type = types.unique {
-          message = ''
-            Only one bootloader can be enabled at a time. This requirement has not
-            been checked until NixOS 22.05. Earlier versions defaulted to the last
-            definition. Change your configuration to enable only one bootloader.
-          '';
-        } (types.either types.str types.package);
-      };
-
       toplevel = mkOption {
         type = types.package;
         readOnly = true;