--- a/lib/default.nix
+++ b/lib/default.nix
@@ -17,7 +17,10 @@
     overlay = mkOptionType {
       name = "nixpkgs-overlay";
       description = "nixpkgs overlay";
-      check = isFunction;
+      check = {
+        __functor = _self: isFunction;
+        isV2MergeCoherent = true;
+      };
       merge = mergeOneOption;
     };
     listOfOverlay = listOf types.overlay;
--- a/modules/secrets-data.nix
+++ b/modules/secrets-data.nix
@@ -115,8 +115,7 @@
   };
 in
 {
-  options.data = mkDataOption (
-    { config, ... }:
+  options.data = mkDataOption ({ config, ... }:
     {
       options = {
         managerKeys = mkOption {
@@ -143,8 +142,7 @@
           toHostSecret = _: secret: (removeAttrs secret [ "owners" ]) // { shared = true; };
         in
         genAttrs hostsWithSharedSecrets (host: mapAttrs toHostSecret (secretsHavingHost host));
-    }
-  );
+    });
   config = {
     assertions =
       (mapAttrsToList (name: secret: {