diff --git a/NixOS.md b/NixOS.md
index d6f53e7..4c1b9dc 100644
--- a/NixOS.md
+++ b/NixOS.md
@@ -495,6 +495,8 @@ A NixOS config example is given in [base.nix](modules/base.nix).
 sudo nix-env --delete-generations +7 --profile /nix/var/nix/profiles/system
 ```
 
+TODO: Should we run `sudo nix-collect-garbage --delete-old` after the above?
+
 ### Garbage collection - Delete system profiles older than X days
 
 * https://nixos.org/manual/nix/stable/package-management/garbage-collection.html