diff --git a/flake.nix b/flake.nix
index a024e478001e677ed1cb51760a3e54749b71ce4a..e81a94a1ae1ab950c3dd8660f2c789adfe6da643 100644
--- a/flake.nix
+++ b/flake.nix
@@ -1,6 +1,6 @@
 {
   description = "head.hackage";
-  inputs.nixpkgs.url = "github:NixOS/nixpkgs";
+  inputs.nixpkgs.url = "github:NixOS/nixpkgs/33e0d99cbedf2acfd7340d2150837fbb28039a64";
   inputs.ghc-artefact-nix.url = "github:mpickering/ghc-artefact-nix";
   inputs.ghc-artefact-nix.flake = false;
   inputs.all-cabal-hashes.url = "github:commercialhaskell/all-cabal-hashes";