diff --git a/tests/functional/tarball.sh b/tests/functional/tarball.sh
index 5d4749eb2..86b8ef2f5 100755
--- a/tests/functional/tarball.sh
+++ b/tests/functional/tarball.sh
@@ -61,6 +61,9 @@ test_tarball .xz xz
 test_tarball .gz gzip
 
 # Test hard links.
+# All entries in tree.tar.gz refer to the same file, and all have the same inode when unpacked by GNU tar.
+# We don't preserve the hard links, because that's an optimization we think is not worth the complexity,
+# so we only make sure that the contents are copied correctly.
 path="$(nix flake prefetch --json "tarball+file://$(pwd)/tree.tar.gz" | jq -r .storePath)"
 [[ $(cat "$path/a/b/foo") = bar ]]
 [[ $(cat "$path/a/b/xyzzy") = bar ]]