diff --git a/flakeModules/flake-module.nix b/flakeModules/flake-module.nix
index aeb74c713..17514d000 100644
--- a/flakeModules/flake-module.nix
+++ b/flakeModules/flake-module.nix
@@ -10,7 +10,8 @@
   flake.flakeModules = {
     clan = import ./clan.nix self;
     default = config.flake.flakeModules.clan;
-    testModule = import ../lib/flake-parts/clan-nixos-test.nix {
+    # testModule is an unstable interface and can change at any time.
+    testModule = lib.modules.importApply ../lib/flake-parts/clan-nixos-test.nix {
       inherit
         self
         inputs
diff --git a/lib/flake-parts/clan-nixos-test.nix b/lib/flake-parts/clan-nixos-test.nix
index 7b0771a8f..40e631929 100644
--- a/lib/flake-parts/clan-nixos-test.nix
+++ b/lib/flake-parts/clan-nixos-test.nix
@@ -24,7 +24,7 @@ in
       in
       {
         options.clan.nixosTests = mkOption {
-          description = "Clan NixOS tests configuration";
+          description = "Unstable interface! Clan NixOS tests configuration";
           type = types.attrsOf types.unspecified;
           default = { };
         };