diff --git a/pkgs/build-support/trivial-builders.nix b/pkgs/build-support/trivial-builders.nix
index 6cd82adf8e7..93b8b1cbc42 100644
--- a/pkgs/build-support/trivial-builders.nix
+++ b/pkgs/build-support/trivial-builders.nix
@@ -157,6 +157,9 @@ rec {
       '';
 
   # Copy a path to the Nix store.
+  # Nix automatically copies files to the store before stringifying paths.
+  # If you need the store path of a file, ${copyPathToStore <path>} can be
+  # shortened to ${<path>}.
   copyPathToStore = builtins.filterSource (p: t: true);
 
   # Copy a list of paths to the Nix store.