diff --git a/README.md b/README.md
index 7247a31..25fb175 100644
--- a/README.md
+++ b/README.md
@@ -69,7 +69,7 @@ Notes:
 - If the board is connected to the local machine, use the ``local_run.sh`` script.
 - To update ``zynq-rs``, update the cargo files as per usual for Rust projects, but also keep ``zynq-rs.nix`` in sync.
 
-[^1]: Thus, on newer version of NixOS, you should run `nix-shell -I nixpkgs=https://github.com/NixOS/nixpkgs/archive/refs/tags/21.05.tar.gz` instead
+[^1]: Thus, on newer version of NixOS, you should run `nix-shell -I nixpkgs=https://github.com/NixOS/nixpkgs/archive/21.05.tar.gz` instead
 
 License
 -------