diff --git a/README.md b/README.md
index 88d2f5f..5a611b9 100644
--- a/README.md
+++ b/README.md
@@ -1,44 +1,29 @@
-# Diamond dependencies with the nixpkgs module system
-
-This flake declares 2 `nixosConfigurations`:
-
-- `.#nixosConfigurations.use-module-binding`
-- `.#nixosConfigurations.use-module-filepath`
-
-They both include the `./vim-option.nix` module twice (simulating a "diamond
-dependency"), but in different ways:
+EDIT: I found <https://github.com/NixOS/nixpkgs/issues/215496> which describes
+this problem.
 
-`use-module-filepath.nix`:
-```nix
-{
-  imports = [
-    ./vim-option.nix
-    ./vim-option.nix
-  ];
+# Diamond dependencies with the nixpkgs module system
 
-  ...
-}
-```
+This flake declares 3 `nixosConfigurations`. They all include a nixos module
+module twice (simulating a "diamond dependency"), but in different ways:
 
-`use-module-binding.nix`:
-```nix
-let vim-option = import ./vim-option.nix;
-in
-{
-  imports = [
-    vim-option
-    vim-option
-  ];
-
-  ...
-}
-```
+- `.#nixosConfigurations.use-module-filepath`: References the module by path twice.
+- `.#nixosConfigurations.use-module-binding`: Imports the module, stashes it in a `let`, and then uses it twice.
+- `.#nixosConfigurations.use-module-binding-with-key`: Like
+  `use-module-binding`, but uses a different module that declares a `key`.
 
 This "double import via a binding" feels like something that's more likely to
 happen as the nix flake ecosystem evolves: someday you're going to end up using
 module A and module B where module B itself uses module A.
 
-Note that `.#nixosConfigurations.use-module-filepath` evaluates fine:
+I don't know if the fix for this is for all modules to declare a human-chosen
+key, or if this is some not-yet-robustly-solved problem. That might be what the
+discussion over on
+<https://github.com/NixOS/nixpkgs/pull/230588#discussion_r1334294197> is
+talking about.
+
+## Demo
+
+### `.#nixosConfigurations.use-module-filepath` works:
 
 ```shell
 $ nix eval .#nixosConfigurations.use-module-filepath.config.system.build.toplevel
@@ -46,7 +31,7 @@ trace: declaring _includeVim
 «derivation /nix/store/dmmxnrhn6c6yibzlcdlwjb1i5akdcjsi-nixos-system-nixos-24.11.20240923.30439d9.drv»
 ```
 
-However, `.#nixosConfigurations.use-module-binding` fails to evaluate:
+### `.#nixosConfigurations.use-module-binding` fails to evaluate:
 
 ```shell
 $ nix eval .#nixosConfigurations.use-module-binding.config.system.build.toplevel
@@ -91,3 +76,11 @@ error:
 
        error: The option `_includeVim' in `/nix/store/vxrd24hjs9k56cjfhchyy57zs0n8kg84-source/use-module-binding.nix' is already declared in `/nix/store/vxrd24hjs9k56cjfhchyy57zs0n8kg84-source/use-module-binding.nix'.
 ```
+
+### `.#nixosConfigurations.use-module-binding-with-key` works:
+
+```shell
+$ nix eval .#nixosConfigurations.use-module-binding-with-key.config.system.build.toplevel
+trace: declaring _includeVim
+«derivation /nix/store/dmmxnrhn6c6yibzlcdlwjb1i5akdcjsi-nixos-system-nixos-24.11.20240923.30439d9.drv»
+```
diff --git a/configs/use-module-binding-with-key.nix b/configs/use-module-binding-with-key.nix
new file mode 100644
index 0000000..1d8391f
--- /dev/null
+++ b/configs/use-module-binding-with-key.nix
@@ -0,0 +1,17 @@
+{
+  lib,
+  pkgs,
+  config,
+  ...
+}:
+let
+  vim-option = import ../shared-module/vim-option-with-key.nix;
+in
+{
+  imports = [
+    vim-option
+    vim-option
+  ];
+
+  environment.systemPackages = lib.mkIf config._includeVim [ pkgs.vim ];
+}
diff --git a/use-module-binding.nix b/configs/use-module-binding.nix
similarity index 75%
rename from use-module-binding.nix
rename to configs/use-module-binding.nix
index 054df89..68bf0f1 100644
--- a/use-module-binding.nix
+++ b/configs/use-module-binding.nix
@@ -5,7 +5,7 @@
   ...
 }:
 let
-  vim-option = import ./vim-option.nix;
+  vim-option = import ../shared-module/vim-option.nix;
 in
 {
   imports = [
diff --git a/use-module-filepath.nix b/configs/use-module-filepath.nix
similarity index 64%
rename from use-module-filepath.nix
rename to configs/use-module-filepath.nix
index 2033d4a..92b66ef 100644
--- a/use-module-filepath.nix
+++ b/configs/use-module-filepath.nix
@@ -6,8 +6,8 @@
 }:
 {
   imports = [
-    ./vim-option.nix
-    ./vim-option.nix
+    ../shared-module/vim-option.nix
+    ../shared-module/vim-option.nix
   ];
 
   environment.systemPackages = lib.mkIf config._includeVim [ pkgs.vim ];
diff --git a/flake.nix b/flake.nix
index 79a91f8..74bbfef 100644
--- a/flake.nix
+++ b/flake.nix
@@ -8,18 +8,25 @@
   outputs =
     { nixpkgs, ... }:
     {
+      nixosConfigurations.use-module-filepath = nixpkgs.lib.nixosSystem {
+        modules = [
+          "${nixpkgs}/nixos/modules/installer/cd-dvd/installation-cd-minimal.nix"
+          ./base.nix
+          ./configs/use-module-filepath.nix
+        ];
+      };
       nixosConfigurations.use-module-binding = nixpkgs.lib.nixosSystem {
         modules = [
           "${nixpkgs}/nixos/modules/installer/cd-dvd/installation-cd-minimal.nix"
           ./base.nix
-          ./use-module-binding.nix
+          ./configs/use-module-binding.nix
         ];
       };
-      nixosConfigurations.use-module-filepath = nixpkgs.lib.nixosSystem {
+      nixosConfigurations.use-module-binding-with-key = nixpkgs.lib.nixosSystem {
         modules = [
           "${nixpkgs}/nixos/modules/installer/cd-dvd/installation-cd-minimal.nix"
           ./base.nix
-          ./use-module-filepath.nix
+          ./configs/use-module-binding-with-key.nix
         ];
       };
     };
diff --git a/shared-module/vim-option-with-key.nix b/shared-module/vim-option-with-key.nix
new file mode 100644
index 0000000..989589d
--- /dev/null
+++ b/shared-module/vim-option-with-key.nix
@@ -0,0 +1,14 @@
+{ lib, ... }:
+{
+  key = "is this a best practice, or is this a workaround? caught in a landslide, no escape from reality";
+  options._includeVim = builtins.trace "declaring _includeVim" (
+    lib.mkOption {
+      internal = true;
+      default = false;
+    }
+  );
+
+  # Interestingly, this does not reproduce the same issue:
+  # options._includeVim = builtins.trace "declaring _includeVim" (lib.mkOption {internal = true;});
+  # config._includeVim = true;
+}
diff --git a/vim-option.nix b/shared-module/vim-option.nix
similarity index 100%
rename from vim-option.nix
rename to shared-module/vim-option.nix