diff --git a/nixpkgs-2105.json b/nixpkgs-2105.json
new file mode 100644
index 0000000000000000000000000000000000000000..d441d00995a78a20cc8677a85ced2a675a9502ae
--- /dev/null
+++ b/nixpkgs-2105.json
@@ -0,0 +1,4 @@
+{ "name": "stable2105"
+, "url": "https://releases.nixos.org/nixos/21.05/nixos-21.05.804.5de44c15758/nixexprs.tar.xz"
+, "sha256": "002zvc16hyrbs0icx1qj255c9dqjpdxx4bhhfjndlj3kwn40by0m"
+}
diff --git a/shell.nix b/shell.nix
index eeea205ec216089b8b2342b0daedaca5ee489d3a..6e46c9ca0feaa3ab6fbd22c1228ec786a49e79b6 100644
--- a/shell.nix
+++ b/shell.nix
@@ -1,8 +1,6 @@
 let
-  nixpkgs-pin = builtins.fromJSON (builtins.readFile ./nixpkgs.json);
-  nixpkgs-src = builtins.fetchTarball nixpkgs-pin;
-  nixpkgs = import nixpkgs-src { };
-  stable2105 = import (builtins.fetchTarball https://nixos.org/channels/nixos-21.05/nixexprs.tar.xz) { };
+  nixpkgs = import (builtins.fetchTarball (builtins.fromJSON (builtins.readFile ./nixpkgs.json))) { };
+  stable2105 = import (builtins.fetchTarball (builtins.fromJSON (builtins.readFile ./nixpkgs-2105.json))) { };
 in
 { pkgs ? nixpkgs }:
 pkgs.mkShell {