diff --git a/README.md b/README.md
index 373c6cd..bb68a05 100644
--- a/README.md
+++ b/README.md
@@ -9,8 +9,14 @@ Canada clusters.  It's layout is modelled after the upstream one.
 
 # Using
 
-To update to the latest version (i.e., the last one for which all
-overlays built successfully) do
+The `nix` module must be loaded
+
+```bash
+module load nix
+```
+
+To update to the latest version of these packages (i.e., the last one
+for which all overlays built successfully) do
 
 ```bash
 nix-channel --update