diff --git a/default.nix b/default.nix
index 8cf2a37..65819e1 100644
--- a/default.nix
+++ b/default.nix
@@ -1,4 +1,4 @@
-{ pkgs ? import ./dep/ci/nixos-20.03 {}
+{ pkgs ? import ./dep/ci/nixos-21.05 {}
 , ghc ? "ghc884"
 }:
 
diff --git a/dep/ci/nixos-21.05/default.nix b/dep/ci/nixos-21.05/default.nix
new file mode 100644
index 0000000..2b4d4ab
--- /dev/null
+++ b/dep/ci/nixos-21.05/default.nix
@@ -0,0 +1,2 @@
+# DO NOT HAND-EDIT THIS FILE
+import (import ./thunk.nix)
\ No newline at end of file
diff --git a/dep/ci/nixos-21.05/github.json b/dep/ci/nixos-21.05/github.json
new file mode 100644
index 0000000..b22278d
--- /dev/null
+++ b/dep/ci/nixos-21.05/github.json
@@ -0,0 +1,8 @@
+{
+  "owner": "NixOS",
+  "repo": "nixpkgs",
+  "branch": "nixos-21.05",
+  "private": false,
+  "rev": "2d6ab6c6b92f7aaf8bc53baba9754b9bfdce56f2",
+  "sha256": "1aafqly1mcqxh0r15mrlsrs4znldhm7cizsmfp3d25lqssay6gjd"
+}
diff --git a/dep/ci/nixos-21.05/thunk.nix b/dep/ci/nixos-21.05/thunk.nix
new file mode 100644
index 0000000..bbf2dc1
--- /dev/null
+++ b/dep/ci/nixos-21.05/thunk.nix
@@ -0,0 +1,9 @@
+# DO NOT HAND-EDIT THIS FILE
+let fetch = { private ? false, fetchSubmodules ? false, owner, repo, rev, sha256, ... }:
+  if !fetchSubmodules && !private then builtins.fetchTarball {
+    url = "https://github.com/${owner}/${repo}/archive/${rev}.tar.gz"; inherit sha256;
+  } else (import <nixpkgs> {}).fetchFromGitHub {
+    inherit owner repo rev sha256 fetchSubmodules private;
+  };
+  json = builtins.fromJSON (builtins.readFile ./github.json);
+in fetch json
\ No newline at end of file