diff --git a/config.nix b/config.nix
index 1cccbb7..9d91476 100644
--- a/config.nix
+++ b/config.nix
@@ -14,6 +14,7 @@ let
           ./modules/system/launchd.nix
           ./modules/environment
           ./modules/launchd
+          ./modules/services/activate-system.nix
           ./modules/programs/tmux.nix
         ];
     };
@@ -36,10 +37,7 @@ let
           pkgs.nox
         ];
 
-      launchd.daemons.activate-system =
-        { serviceConfig.Program = "${config.system.build.activate}";
-          serviceConfig.RunAtLoad = true;
-        };
+      services.activate-system.enable = true;
 
       launchd.daemons.nix-daemon =
         { serviceConfig.Program = "/nix/var/nix/profiles/default/bin/nix-daemon";
@@ -121,7 +119,7 @@ let
             'build')   nix-build '<nixpkgs>' -A nixdarwin.toplevel "$@" ;;
             'repl')    nix-repl "$HOME/.nixpkgs/config.nix" "$@" ;;
             'shell')   nix-shell '<nixpkgs>' -p nixdarwin.toplevel --run '${pkgs.lnl.zsh}/bin/zsh -l' "$@" ;;
-            'switch')  sudo nix-env --profile /nix/var/nix/profiles/system --set $(nix-build --no-out-link '<nixpkgs>' -A nixdarwin.toplevel) && nix-shell '<nixpkgs>' -A nixdarwin.toplevel --run 'sudo $out/activate' && exec ${pkgs.lnl.zsh}/bin/zsh -l ;;
+            'switch')  sudo nix-env --profile ${config.system.profile} --set $(nix-build --no-out-link '<nixpkgs>' -A nixdarwin.toplevel) && nix-shell '<nixpkgs>' -A nixdarwin.toplevel --run 'sudo $out/activate' && exec ${pkgs.lnl.zsh}/bin/zsh -l ;;
           esac
         }
 
diff --git a/modules/services/activate-system.nix b/modules/services/activate-system.nix
new file mode 100644
index 0000000..a92576f
--- /dev/null
+++ b/modules/services/activate-system.nix
@@ -0,0 +1,47 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+
+  cfg = config.services.activate-system;
+
+  activateScript = pkgs.writeScript "activate-system" ''
+    #! ${pkgs.stdenv.shell}
+
+    # Make this configuration the current configuration.
+    # The readlink is there to ensure that when $systemConfig = /system
+    # (which is a symlink to the store), /run/current-system is still
+    # used as a garbage collection root.
+    ln -sfn $(cat ${config.system.profile}/systemConfig) /run/current-system
+
+    # Prevent the current configuration from being garbage-collected.
+    ln -sfn /run/current-system /nix/var/nix/gcroots/current-system
+  '';
+
+in
+
+{
+  options = {
+    services.activate-system = {
+
+      enable = mkOption {
+        type = types.bool;
+        default = false;
+        description = ''
+          Whether to activate system at boot time.
+        '';
+      };
+
+    };
+  };
+
+  config = {
+
+    launchd.daemons.activate-system = mkIf cfg.enable {
+      serviceConfig.Program = "${activateScript}";
+      serviceConfig.RunAtLoad = true;
+    };
+
+  };
+}
diff --git a/modules/system/activation-scripts.nix b/modules/system/activation-scripts.nix
index fe3131d..fda882f 100644
--- a/modules/system/activation-scripts.nix
+++ b/modules/system/activation-scripts.nix
@@ -34,19 +34,6 @@ in
 
   config = {
 
-    system.build.activate = pkgs.writeScript "activate-system" ''
-      #! ${pkgs.stdenv.shell}
-
-      # Make this configuration the current configuration.
-      # The readlink is there to ensure that when $systemConfig = /system
-      # (which is a symlink to the store), /run/current-system is still
-      # used as a garbage collection root.
-      ln -sfn $(cat /nix/var/nix/profiles/system/systemConfig) /run/current-system
-
-      # Prevent the current configuration from being garbage-collected.
-      ln -sfn /run/current-system /nix/var/nix/gcroots/current-system
-    '';
-
     system.activationScripts.script.text = ''
       #! ${pkgs.stdenv.shell}
 
diff --git a/modules/system/default.nix b/modules/system/default.nix
index 9cf190e..d1d9f72 100644
--- a/modules/system/default.nix
+++ b/modules/system/default.nix
@@ -27,6 +27,14 @@ in
       '';
     };
 
+    system.profile = mkOption {
+      type = types.path;
+      default = "/nix/var/nix/profiles/system";
+      description = ''
+        Profile to use for the system.
+      '';
+    };
+
     system.nixdarwinLabel = mkOption {
       type = types.str;
       default = "16.09";