diff --git a/pkgs/nix-tools/darwin-rebuild.sh b/pkgs/nix-tools/darwin-rebuild.sh
index aa066865..c0ea55b7 100644
--- a/pkgs/nix-tools/darwin-rebuild.sh
+++ b/pkgs/nix-tools/darwin-rebuild.sh
@@ -18,7 +18,11 @@ showSyntax() {
 }
 
 sudo() {
+  # REMOVEME when support for macOS 10.13 is dropped
+  # macOS 10.13 does not support sudo --preserve-env so we make this conditional
   if command sudo --help | grep -- --preserve-env= >/dev/null; then
+    # We use `env` before our command to ensure the preserved PATH gets checked
+    # when trying to resolve the command to execute
     command sudo -H --preserve-env=PATH env "$@"
   else
     command sudo -H "$@"