diff --git a/dev/flake-module.nix b/dev/flake-module.nix
index 60da698..d4a8237 100644
--- a/dev/flake-module.nix
+++ b/dev/flake-module.nix
@@ -6,7 +6,7 @@
     ../site/flake-module.nix
   ];
   systems = [ "x86_64-linux" "aarch64-darwin" ];
-  perSystem = system: { config, self', inputs', pkgs, ... }: {
+  perSystem = { config, self', inputs', pkgs, ... }: {
 
     devShells.default = pkgs.mkShell {
       nativeBuildInputs = [
diff --git a/dev/flake.lock b/dev/flake.lock
index 2dcc47f..2a33091 100644
--- a/dev/flake.lock
+++ b/dev/flake.lock
@@ -20,11 +20,11 @@
         "nixpkgs": "nixpkgs"
       },
       "locked": {
-        "lastModified": 1653415319,
-        "narHash": "sha256-h+YUX7ZYujf73KL1R07LsEnhV7uV8oxSKEhH4bDj0Jc=",
+        "lastModified": 1653487348,
+        "narHash": "sha256-lWqxXMRqO8blpwhH2qvrFBVp6aZ7V+Z3xTqkNWKyLQw=",
         "owner": "hercules-ci",
         "repo": "hercules-ci-effects",
-        "rev": "1f904af1824e7393702daaf40a8fed56ebead0d7",
+        "rev": "0ab66b56d3f2b40ddfd981899d1757773632075f",
         "type": "github"
       },
       "original": {
@@ -73,11 +73,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1638351750,
-        "narHash": "sha256-90OHC+11DIHD1QyMIPUuM3n6zjH5Mhc8RBZa0h8969A=",
+        "lastModified": 1653494825,
+        "narHash": "sha256-hMhnHZGRlJBX3yWIvxuYIBo4g+XQy/DJ4z7ti0IX7x0=",
         "owner": "hercules-ci",
         "repo": "pre-commit-hooks.nix",
-        "rev": "3bb289628867ac40fc9e7c514f8266b1ce8c0910",
+        "rev": "89b64b7aca69fbd2957232d6a5a36bb93ad59d4b",
         "type": "github"
       },
       "original": {
diff --git a/lib.nix b/lib.nix
index bb693e5..0d728f3 100644
--- a/lib.nix
+++ b/lib.nix
@@ -2,8 +2,17 @@
 let
   inherit (lib)
     mkOption
+    mkOptionType
+    defaultFunctor
+    isAttrs
+    isFunction
+    showOption
     types
     ;
+  inherit (lib.types)
+    path
+    submoduleWith
+    ;
 
   # Polyfill functionTo to make sure it has type merging.
   # Remove 2022-12
@@ -26,6 +35,32 @@ let
         nestedTypes.elemType = elemType;
       };
 
+  # Polyfill https://github.com/NixOS/nixpkgs/pull/163617
+  deferredModuleWith = lib.deferredModuleWith or (
+    attrs@{ staticModules ? [ ] }: mkOptionType {
+      name = "deferredModule";
+      description = "module";
+      check = x: isAttrs x || isFunction x || path.check x;
+      merge = loc: defs: staticModules ++ map (def: lib.setDefaultModuleLocation "${def.file}, via option ${showOption loc}" def.value) defs;
+      inherit (submoduleWith { modules = staticModules; })
+        getSubOptions
+        getSubModules;
+      substSubModules = m: deferredModuleWith (attrs // {
+        staticModules = m;
+      });
+      functor = defaultFunctor "deferredModuleWith" // {
+        type = deferredModuleWith;
+        payload = {
+          inherit staticModules;
+        };
+        binOp = lhs: rhs: {
+          staticModules = lhs.staticModules ++ rhs.staticModules;
+        };
+      };
+    }
+  );
+
+
   flake-parts-lib = {
     evalFlakeModule =
       { self
@@ -53,10 +88,9 @@ let
 
     mkPerSystemType =
       module:
-      functionTo (types.submoduleWith {
-        modules = [ module ];
-        shorthandOnlyDefinesConfig = false;
-      });
+      deferredModuleWith {
+        staticModules = [ module ];
+      };
 
     mkPerSystemOption =
       module:
diff --git a/modules/nixpkgs.nix b/modules/nixpkgs.nix
index d3870fc..44df915 100644
--- a/modules/nixpkgs.nix
+++ b/modules/nixpkgs.nix
@@ -13,7 +13,7 @@
 #
 {
   config = {
-    perSystem = _: { inputs', lib, ... }: {
+    perSystem = { inputs', lib, ... }: {
       config = {
         _module.args.pkgs = lib.mkOptionDefault (
           builtins.seq
diff --git a/modules/perSystem.nix b/modules/perSystem.nix
index 446adee..1e9be2c 100644
--- a/modules/perSystem.nix
+++ b/modules/perSystem.nix
@@ -34,6 +34,14 @@ in
           _module.args.self' = rootConfig.perInput system self;
         };
       });
+      apply = modules: system:
+        (lib.evalModules {
+          inherit modules;
+          prefix = [ "perSystem" system ];
+          specialArgs = {
+            inherit system;
+          };
+        }).config;
     };
 
     allSystems = mkOption {
@@ -44,7 +52,6 @@ in
   };
 
   config = {
-    perSystem = system: { _module.args.system = system; };
     allSystems = genAttrs config.systems config.perSystem;
     # TODO: Sub-optimal error message. Get Nix to support a memoization primop, or get Nix Flakes to support systems properly or get Nix Flakes to add a name to flakes.
     _module.args.getSystem = system: config.allSystems.${system} or (builtins.trace "using non-memoized system ${system}" config.perSystem system);
diff --git a/site/flake-module.nix b/site/flake-module.nix
index 4814b57..6cf4d8c 100644
--- a/site/flake-module.nix
+++ b/site/flake-module.nix
@@ -1,5 +1,5 @@
 { ... }: {
-  perSystem = system: { config, self', inputs', pkgs, lib, ... }:
+  perSystem = { config, self', inputs', pkgs, lib, ... }:
     let
       inherit (lib) filter any hasPrefix concatMap removePrefix;
 
diff --git a/template/default/flake.nix b/template/default/flake.nix
index f0d6be7..9277a70 100644
--- a/template/default/flake.nix
+++ b/template/default/flake.nix
@@ -17,7 +17,7 @@
 
       ];
       systems = [ "x86_64-linux" "aarch64-darwin" ];
-      perSystem = system: { config, self', inputs', pkgs, ... }: {
+      perSystem = { config, self', inputs', pkgs, system, ... }: {
         # Per-system attributes can be defined here. The self' and inputs'
         # module parameters provide easy access to attributes of the same
         # system.
diff --git a/template/multi-module/flake.nix b/template/multi-module/flake.nix
index 2964b21..91e334c 100644
--- a/template/multi-module/flake.nix
+++ b/template/multi-module/flake.nix
@@ -13,7 +13,7 @@
         ./hello/flake-module.nix
       ];
       systems = [ "x86_64-linux" "aarch64-darwin" ];
-      perSystem = system: { config, self', inputs', ... }: {
+      perSystem = { config, self', inputs', ... }: {
         # Per-system attributes can be defined here. The self' and inputs'
         # module parameters provide easy access to attributes of the same
         # system.
diff --git a/template/multi-module/hello/flake-module.nix b/template/multi-module/hello/flake-module.nix
index 8629bfe..55066f0 100644
--- a/template/multi-module/hello/flake-module.nix
+++ b/template/multi-module/hello/flake-module.nix
@@ -1,7 +1,7 @@
 # Definitions can be imported from a separate file like this one
 
 { self, ... }: {
-  perSystem = system: { config, self', inputs', pkgs, ... }: {
+  perSystem = { config, self', inputs', pkgs, ... }: {
     # Definitions like this are entirely equivalent to the ones
     # you may have directly in flake.nix.
     packages.hello = pkgs.hello;