diff --git a/README.md b/README.md
index bb68a05..af2d6d4 100644
--- a/README.md
+++ b/README.md
@@ -38,7 +38,7 @@ To install (or update) a package, specify the packages attribute to
 `nix-env` using the `--attr` option
 
 ```bash
-nix-env --install --attr attribute
+nix-env --install --attr nixpkgs.attribute
 ```
 
 where `attribute` is replaced with the attribute that designates the
@@ -75,6 +75,7 @@ nix-env --rollback
 
 A development environment consisting of a given set of packages can be
 entered using the `nix-shell` command with the `--packages` option
+(unlike `nix-env`, this automatically uses the `nixpkgs` channel)
 
 ```bash
 nix-shell --packages attribute ...