diff --git a/modules/system/meta/domains.nix b/modules/system/meta/domains.nix
index 9789ee2..078f935 100644
--- a/modules/system/meta/domains.nix
+++ b/modules/system/meta/domains.nix
@@ -6,29 +6,6 @@
 }:
 let
   cfg = config.meta.domains;
-
-  duplicatedDomains =
-    self.nixosConfigurations
-    |> lib.mapAttrsToList (_: value: value.options.meta.domains.list.definitionsWithLocations)
-    |> lib.concatLists
-    |> lib.concatMap (
-      entry:
-      map (domain: {
-        file = entry.file;
-        inherit domain;
-      }) entry.value
-    )
-    |> lib.groupBy (entry: toString entry.domain)
-    |> lib.filterAttrs (domain: entries: lib.length entries > 1);
-
-  errorMessage =
-    duplicatedDomains
-    |> lib.mapAttrsToList (
-      domain: entries:
-      "Duplicate domain \"${domain}\" found in:\n"
-      + lib.concatMapStrings (entry: "  - ${entry.file}\n") entries
-    )
-    |> lib.concatStrings;
 in
 {
   options.meta.domains = {
@@ -37,17 +14,51 @@ in
       default = [ ];
       internal = true;
     };
+    globalList = lib.mkOption {
+      type = lib.types.listOf lib.types.nonEmptyStr;
+      default =
+        self.nixosConfigurations
+        |> lib.mapAttrsToList (_: value: value.config.meta.domains.list)
+        |> lib.concatLists;
+      internal = true;
+      readOnly = true;
+    };
     assertUnique = lib.mkEnableOption "" // {
       default = true;
     };
   };
 
   config = lib.mkIf cfg.assertUnique {
-    assertions = [
-      {
-        assertion = duplicatedDomains == { };
-        message = errorMessage;
-      }
-    ];
+    assertions =
+      let
+        duplicateDomains =
+          self.nixosConfigurations
+          |> lib.mapAttrsToList (_: value: value.options.meta.domains.list.definitionsWithLocations)
+          |> lib.concatLists
+          |> lib.concatMap (
+            entry:
+            map (domain: {
+              file = entry.file;
+              inherit domain;
+            }) entry.value
+          )
+          |> lib.groupBy (entry: toString entry.domain)
+          |> lib.filterAttrs (domain: entries: lib.length entries > 1);
+
+        errorMessage =
+          duplicateDomains
+          |> lib.mapAttrsToList (
+            domain: entries:
+            "Duplicate domain \"${domain}\" found in:\n"
+            + lib.concatMapStrings (entry: "  - ${entry.file}\n") entries
+          )
+          |> lib.concatStrings;
+      in
+      [
+        {
+          assertion = duplicateDomains == { };
+          message = errorMessage;
+        }
+      ];
   };
 }
diff --git a/modules/system/meta/ports.nix b/modules/system/meta/ports.nix
index 138fea7..4c7fde1 100644
--- a/modules/system/meta/ports.nix
+++ b/modules/system/meta/ports.nix
@@ -6,26 +6,6 @@
 }:
 let
   cfg = config.meta.ports;
-
-  duplicatedPorts =
-    options.meta.ports.list.definitionsWithLocations
-    |> lib.concatMap (
-      entry:
-      map (port: {
-        file = entry.file;
-        inherit port;
-      }) entry.value
-    )
-    |> lib.groupBy (entry: toString entry.port)
-    |> lib.filterAttrs (port: entries: lib.length entries > 1);
-
-  errorMessage =
-    duplicatedPorts
-    |> lib.mapAttrsToList (
-      port: entries:
-      "Duplicate port ${port} found in:\n" + lib.concatMapStrings (entry: "  - ${entry.file}\n") entries
-    )
-    |> lib.concatStrings;
 in
 {
   options.meta.ports = {
@@ -40,11 +20,33 @@ in
   };
 
   config = lib.mkIf cfg.assertUnique {
-    assertions = [
-      {
-        assertion = duplicatedPorts == { };
-        message = errorMessage;
-      }
-    ];
+    assertions =
+      let
+        duplicatePorts =
+          options.meta.ports.list.definitionsWithLocations
+          |> lib.concatMap (
+            entry:
+            map (port: {
+              inherit (entry) file;
+              inherit port;
+            }) entry.value
+          )
+          |> lib.groupBy (entry: toString entry.port)
+          |> lib.filterAttrs (port: entries: lib.length entries > 1);
+
+        errorMessage =
+          duplicatePorts
+          |> lib.mapAttrsToList (
+            port: entries:
+            "Duplicate port ${port} found in:\n" + lib.concatMapStrings (entry: "  - ${entry.file}\n") entries
+          )
+          |> lib.concatStrings;
+      in
+      [
+        {
+          assertion = duplicatePorts == { };
+          message = errorMessage;
+        }
+      ];
   };
 }