diff --git a/shell.nix b/shell.nix
index 7b97e75..1def6db 100644
--- a/shell.nix
+++ b/shell.nix
@@ -1,4 +1,15 @@
-{ pkgs ? import <nixpkgs> { }
+{ pkgs ? (
+    let
+      inherit (builtins) fromJSON readFile;
+      flakeLock = fromJSON (readFile ./flake.lock);
+      locked = flakeLock.nodes.nixpkgs.locked;
+      nixpkgs = assert locked.type == "github"; builtins.fetchTarball {
+        url = "https://github.com/${locked.owner}/${locked.repo}/archive/${locked.rev}.tar.gz";
+        sha256 = locked.narHash;
+      };
+    in
+    import nixpkgs { }
+  )
 , srcDir ? null
 }: