diff --git a/version-rust/README.md b/version-rust/README.md
index b5a3728..66e4baf 100644
--- a/version-rust/README.md
+++ b/version-rust/README.md
@@ -91,6 +91,9 @@ Notes:
 
 - `tar`/`gz`/`bz2`/`xz` extraction shells out to the system binaries
   (7z CLI in python); 7z/zip/rar use native Rust.
+- The extractor also recognizes `.tgz` (a gzip-compressed tar). The python
+  suffix set never included it, so python left those files unextracted; this
+  is a deliberate Rust-only addition.
 - `fs::copy` fallback in the sorter does not preserve mtime
   (python `shutil.copy2` does).
 - state.json omits `"files": []` for records without files