diff --git a/dev/default.nix b/dev/default.nix
index 6af149b..d6d28a4 100644
--- a/dev/default.nix
+++ b/dev/default.nix
@@ -1,6 +1,6 @@
 let
   flake = builtins.getFlake (toString ./.);
-  fmc-lib = import ../lib.nix { inherit (flake.inputs.nixpkgs) lib; };
+  fmc-lib = (builtins.getFlake (toString ../.)).lib;
   self = {
     inherit (flake) inputs;
     outPath = ../.; # used by pre-commit module, etc
diff --git a/lib.nix b/lib.nix
index 0d728f3..2d38daa 100644
--- a/lib.nix
+++ b/lib.nix
@@ -98,6 +98,34 @@ let
         type = flake-parts-lib.mkPerSystemType module;
       };
 
+    # Helper function for defining a per-system option that
+    # gets transposed by the usual flake system logic to a
+    # top-level flake attribute.
+    mkTransposedPerSystemModule = { name, option, file }: {
+      _file = file;
+
+      options = {
+        flake = flake-parts-lib.mkSubmoduleOptions {
+          ${name} = mkOption {
+            type = types.lazyAttrsOf option.type;
+            default = { };
+            description = lib.mdDoc ''
+              See {option}`perSystem.${name}` for description and examples.
+            '';
+          };
+        };
+
+        perSystem = flake-parts-lib.mkPerSystemOption {
+          _file = file;
+
+          options.${name} = option;
+        };
+      };
+
+      config = {
+        transposition.${name} = { };
+      };
+    };
   };
 
 in
diff --git a/modules/apps.nix b/modules/apps.nix
index e411fd6..a3f8219 100644
--- a/modules/apps.nix
+++ b/modules/apps.nix
@@ -1,15 +1,11 @@
 { config, lib, flake-parts-lib, ... }:
 let
   inherit (lib)
-    filterAttrs
-    mapAttrs
     mkOption
-    optionalAttrs
     types
     ;
   inherit (flake-parts-lib)
-    mkSubmoduleOptions
-    mkPerSystemOption
+    mkTransposedPerSystemModule
     ;
 
   programType = lib.types.coercedTo derivationType getExe lib.types.str;
@@ -44,43 +40,19 @@ let
     };
   };
 in
-{
-  options = {
-    flake = mkSubmoduleOptions {
-      apps = mkOption {
-        type = types.lazyAttrsOf (types.lazyAttrsOf appType);
-        default = { };
-        description = ''
-          Programs runnable with nix run <literal>.#&lt;name></literal>.
-        '';
-        example = lib.literalExpression or lib.literalExample ''
-          {
-            x86_64-linux.default.program = "''${config.packages.hello}/bin/hello";
-          }
-        '';
-      };
-    };
-
-    perSystem = mkPerSystemOption
-      ({ config, system, ... }: {
-        options = {
-          apps = mkOption {
-            type = types.lazyAttrsOf appType;
-            default = { };
-            description = ''
-              Programs runnable with nix run <literal>.#&lt;name></literal>.
-            '';
-            example = lib.literalExpression or lib.literalExample ''
-              {
-                default.program = "''${config.packages.hello}/bin/hello";
-              }
-            '';
-          };
-        };
-      });
-
-  };
-  config = {
-    transposition.apps = { };
+mkTransposedPerSystemModule {
+  name = "apps";
+  option = mkOption {
+    type = types.lazyAttrsOf appType;
+    default = { };
+    description = ''
+      Programs runnable with nix run <literal>.#&lt;name></literal>.
+    '';
+    example = lib.literalExpression or lib.literalExample ''
+      {
+        default.program = "''${config.packages.hello}/bin/hello";
+      }
+    '';
   };
+  file = ./apps.nix;
 }
diff --git a/modules/checks.nix b/modules/checks.nix
index 4fbb0af..12dde09 100644
--- a/modules/checks.nix
+++ b/modules/checks.nix
@@ -1,44 +1,21 @@
 { config, lib, flake-parts-lib, ... }:
 let
   inherit (lib)
-    filterAttrs
-    mapAttrs
     mkOption
-    optionalAttrs
     types
     ;
   inherit (flake-parts-lib)
-    mkSubmoduleOptions
-    mkPerSystemOption
+    mkTransposedPerSystemModule
     ;
 in
-{
-  options = {
-    flake = mkSubmoduleOptions {
-      checks = mkOption {
-        type = types.lazyAttrsOf (types.lazyAttrsOf types.package);
-        default = { };
-        description = ''
-          Derivations to be built by nix flake check.
-        '';
-      };
-    };
-
-    perSystem = mkPerSystemOption ({ config, system, ... }: {
-      _file = ./checks.nix;
-      options = {
-        checks = mkOption {
-          type = types.lazyAttrsOf types.package;
-          default = { };
-          description = ''
-            Derivations to be built by nix flake check.
-          '';
-        };
-      };
-    });
-
-  };
-  config = {
-    transposition.checks = { };
+mkTransposedPerSystemModule {
+  name = "checks";
+  option = mkOption {
+    type = types.lazyAttrsOf types.package;
+    default = { };
+    description = ''
+      Derivations to be built by nix flake check.
+    '';
   };
+  file = ./checks.nix;
 }
diff --git a/modules/devShells.nix b/modules/devShells.nix
index ecc53b3..7ebbeb6 100644
--- a/modules/devShells.nix
+++ b/modules/devShells.nix
@@ -1,45 +1,22 @@
 { config, lib, flake-parts-lib, ... }:
 let
   inherit (lib)
-    filterAttrs
-    mapAttrs
     mkOption
-    optionalAttrs
     types
     ;
   inherit (flake-parts-lib)
-    mkSubmoduleOptions
-    mkPerSystemOption
+    mkTransposedPerSystemModule
     ;
 in
-{
-  options = {
-    flake = mkSubmoduleOptions {
-      devShells = mkOption {
-        type = types.lazyAttrsOf (types.lazyAttrsOf types.package);
-        default = { };
-        description = ''
-          Per system an attribute set of packages used as shells.
-          <literal>nix develop .#&lt;name></literal> will run <literal>devShells.&lt;system>.&lt;name></literal>.
-        '';
-      };
-    };
-
-    perSystem = mkPerSystemOption
-      ({ config, system, ... }: {
-        options = {
-          devShells = mkOption {
-            type = types.lazyAttrsOf types.package;
-            default = { };
-            description = ''
-              An attribute set of packages to be built by <literal>nix develop .#&lt;name></literal>.
-              <literal>nix build .#&lt;name></literal> will run <literal>devShells.&lt;name></literal>.
-            '';
-          };
-        };
-      });
-  };
-  config = {
-    transposition.devShells = { };
+mkTransposedPerSystemModule {
+  name = "devShells";
+  option = mkOption {
+    type = types.lazyAttrsOf types.package;
+    default = { };
+    description = ''
+      An attribute set of packages to be built by <literal>nix develop .#&lt;name></literal>.
+      <literal>nix build .#&lt;name></literal> will run <literal>devShells.&lt;name></literal>.
+    '';
   };
+  file = ./devShells.nix;
 }
diff --git a/modules/formatter.nix b/modules/formatter.nix
index a63a9ba..d5b0435 100644
--- a/modules/formatter.nix
+++ b/modules/formatter.nix
@@ -1,55 +1,21 @@
 { config, lib, flake-parts-lib, ... }:
 let
   inherit (lib)
-    filterAttrs
-    mapAttrs
     mkOption
-    optionalAttrs
     types
     ;
   inherit (flake-parts-lib)
-    mkSubmoduleOptions
-    mkPerSystemOption
+    mkTransposedPerSystemModule
     ;
 in
-{
-  options = {
-    flake = mkSubmoduleOptions {
-      formatter = mkOption {
-        type = types.lazyAttrsOf types.package;
-        default = { };
-        description = ''
-          Per system package used by <literal>nix fmt</literal>.
-        '';
-      };
-    };
-
-    perSystem = mkPerSystemOption ({ config, ... }: {
-      _file = ./formatter.nix;
-      options = {
-        formatter = mkOption {
-          type = types.nullOr types.package;
-          default = null;
-          description = ''
-            A package used by <literal>nix fmt</literal>.
-          '';
-        };
-      };
-    });
-  };
-  config = {
-    flake.formatter =
-      mapAttrs
-        (k: v: v.formatter)
-        (filterAttrs
-          (k: v: v.formatter != null)
-          config.allSystems
-        );
-
-    perInput = system: flake:
-      optionalAttrs (flake?formatter.${system}) {
-        formatter = flake.formatter.${system};
-      };
-
+mkTransposedPerSystemModule {
+  name = "formatter";
+  option = mkOption {
+    type = types.nullOr types.package;
+    default = null;
+    description = ''
+      A package used by <literal>nix fmt</literal>.
+    '';
   };
+  file = ./formatter.nix;
 }
diff --git a/modules/legacyPackages.nix b/modules/legacyPackages.nix
index eedc075..f07ab16 100644
--- a/modules/legacyPackages.nix
+++ b/modules/legacyPackages.nix
@@ -1,43 +1,21 @@
 { config, lib, flake-parts-lib, ... }:
 let
   inherit (lib)
-    filterAttrs
-    mapAttrs
     mkOption
-    optionalAttrs
     types
     ;
   inherit (flake-parts-lib)
-    mkSubmoduleOptions
-    mkPerSystemOption
+    mkTransposedPerSystemModule
     ;
 in
-{
-  options = {
-    flake = mkSubmoduleOptions {
-      legacyPackages = mkOption {
-        type = types.lazyAttrsOf (types.lazyAttrsOf types.raw);
-        default = { };
-        description = ''
-          Per system, an attribute set of unmergeable values. This is also used by <literal>nix build .#&lt;attrpath></literal>.
-        '';
-      };
-    };
-
-    perSystem = mkPerSystemOption ({ config, ... }: {
-      options = {
-        legacyPackages = mkOption {
-          type = types.lazyAttrsOf types.raw;
-          default = { };
-          description = ''
-            An attribute set of unmergeable values. This is also used by <literal>nix build .#&lt;attrpath></literal>.
-          '';
-        };
-      };
-    });
-  };
-
-  config = {
-    transposition.legacyPackages = { };
+mkTransposedPerSystemModule {
+  name = "legacyPackages";
+  option = mkOption {
+    type = types.lazyAttrsOf types.raw;
+    default = { };
+    description = ''
+      An attribute set of unmergeable values. This is also used by <literal>nix build .#&lt;attrpath></literal>.
+    '';
   };
+  file = ./legacyPackages.nix;
 }
diff --git a/modules/packages.nix b/modules/packages.nix
index 05fea46..a6a22c5 100644
--- a/modules/packages.nix
+++ b/modules/packages.nix
@@ -1,45 +1,22 @@
 { config, lib, flake-parts-lib, ... }:
 let
   inherit (lib)
-    filterAttrs
-    mapAttrs
     mkOption
-    optionalAttrs
     types
     ;
   inherit (flake-parts-lib)
-    mkSubmoduleOptions
-    mkPerSystemOption
+    mkTransposedPerSystemModule
     ;
 in
-{
-  options = {
-    flake = mkSubmoduleOptions {
-      packages = mkOption {
-        type = types.lazyAttrsOf (types.lazyAttrsOf types.package);
-        default = { };
-        description = ''
-          Per system an attribute set of packages.
-          <literal>nix build .#&lt;name></literal> will build <literal>packages.&lt;system>.&lt;name></literal>.
-        '';
-      };
-    };
-
-    perSystem = mkPerSystemOption ({ config, ... }: {
-      _file = ./packages.nix;
-      options = {
-        packages = mkOption {
-          type = types.lazyAttrsOf types.package;
-          default = { };
-          description = ''
-            An attribute set of packages to be built by <literal>nix build .#&lt;name></literal>.
-            <literal>nix build .#&lt;name></literal> will build <literal>packages.&lt;name></literal>.
-          '';
-        };
-      };
-    });
-  };
-  config = {
-    transposition.packages = { };
+mkTransposedPerSystemModule {
+  name = "packages";
+  option = mkOption {
+    type = types.lazyAttrsOf types.package;
+    default = { };
+    description = ''
+      An attribute set of packages to be built by <literal>nix build .#&lt;name></literal>.
+      <literal>nix build .#&lt;name></literal> will build <literal>packages.&lt;name></literal>.
+    '';
   };
+  file = ./packages.nix;
 }