diff --git a/lib/inventory/build-inventory/interface.nix b/lib/inventory/build-inventory/interface.nix
index 2e0f713af..01c25c37b 100644
--- a/lib/inventory/build-inventory/interface.nix
+++ b/lib/inventory/build-inventory/interface.nix
@@ -343,6 +343,7 @@ in
         }
       );
       default = { };
+      apply = lib.warn "Inventory.instances and related features are still under development. Please use with care.";
     };
     services = lib.mkOption {
       description = ''