diff --git a/flake.lock b/flake.lock
index 7617c3a..6bf8405 100644
--- a/flake.lock
+++ b/flake.lock
@@ -42,11 +42,11 @@
         "nixpkgs": "nixpkgs"
       },
       "locked": {
-        "lastModified": 1729966280,
-        "narHash": "sha256-8G0n9POJW2zITB1m2h9+0GHA6lNlfsd2kssEqYLfK/U=",
+        "lastModified": 1729990097,
+        "narHash": "sha256-3RUciZy/VMbyp9v1f8oba/oQ8bWWVh2+1wsuUah3ryE=",
         "owner": "lenianiva",
         "repo": "lean4-nix",
-        "rev": "169dfe5e5db6038801ecfdbe4391cb14c5e8d454",
+        "rev": "6919763f186c7b0d39907203a649078ff3a4eb71",
         "type": "github"
       },
       "original": {
diff --git a/flake.nix b/flake.nix
index a2d0263..2c1a76e 100644
--- a/flake.nix
+++ b/flake.nix
@@ -28,7 +28,7 @@
     perSystem = { system, pkgs, ... }: let
       pkgs = import nixpkgs {
         inherit system;
-        overlays = [ lean4-nix.tags."v4.12.0" ];
+        overlays = [ (lean4-nix.readToolchainFile ./lean-toolchain) ];
       };
       lspecLib = pkgs.lean.buildLeanPackage {
         name = "LSpec";