diff --git a/lib/services/lib.nix b/lib/services/lib.nix
index 37249512b65b..7c235e066802 100644
--- a/lib/services/lib.nix
+++ b/lib/services/lib.nix
@@ -52,6 +52,8 @@ rec {
     let
       modularServiceConfiguration = lib.services.configure {
         serviceManagerPkgs = pkgs;
+        # To load a different portable service base, set `baseModules` instead:
+        #   baseModules = [ (lib.importService { inherit pkgs; }) ];
         extraRootModules = [
           ./launchd-service.nix    # launchd-specific options (plist generation, etc.)
         ];
@@ -80,18 +82,27 @@ rec {
     `serviceManagerPkgs`
 
     : 1\. A Nixpkgs instance used for built-in logic such as converting
-    `configData.<path>.text` to a store path.
+    `configData.<path>.text` to a store path. Required unless `baseModules`
+    is set.
+
+    `baseModules`
+
+    : 2\. Modules that replace the portable service base. They are loaded
+    into the "root" service submodule and must handle propagation to
+    sub-`services` themselves. Defaults to the portable service base of
+    this Nixpkgs. Set it to supply a different one, for example a
+    `service.nix` pinned from another Nixpkgs.
 
     `extraRootModules`
 
-    : 2\. Modules to be loaded into the "root" service submodule, but not
+    : 3\. Modules to be loaded into the "root" service submodule, but not
     into its sub-`services`. That's the modules' own responsibility.
     Typically contains service-manager-specific option modules
     (e.g. systemd unit options, launchd plist options).
 
     `extraRootSpecialArgs`
 
-    : 3\. Fixed module arguments provided alongside `extraRootModules`.
+    : 4\. Fixed module arguments provided alongside `extraRootModules`.
 
     # Output
 
@@ -101,17 +112,15 @@ rec {
   */
   configure =
     {
-      serviceManagerPkgs,
+      serviceManagerPkgs ? throw "lib.services.configure: `serviceManagerPkgs` is required unless `baseModules` is set",
+      baseModules ? [ (lib.importService { pkgs = serviceManagerPkgs; }) ],
       extraRootModules ? [ ],
       extraRootSpecialArgs ? { },
     }:
     let
-      modules = [
-        (lib.modules.importApply ./service.nix { pkgs = serviceManagerPkgs; })
-      ];
       serviceSubmodule = types.submoduleWith {
         class = "service";
-        modules = modules ++ extraRootModules;
+        modules = baseModules ++ extraRootModules;
         specialArgs = extraRootSpecialArgs;
       };
     in