diff --git a/shell.nix b/shell.nix
index 54b7182..e20f166 100644
--- a/shell.nix
+++ b/shell.nix
@@ -1,5 +1,6 @@
 let
   nixpkgs = import (fetchTarball {
+    # Run `cachix use jechol` to use compiled binary cache.
     url = "https://github.com/jechol/nixpkgs/archive/21.11-otp24-no-jit.tar.gz";
     sha256 = "sha256:1lka707hrnkp70vny99m9fmp4a8136vl7addmpfsdvkwb81d1jk9";
   }) { };