diff --git a/package_python_function/packager.py b/package_python_function/packager.py
index 20687d0..8303370 100644
--- a/package_python_function/packager.py
+++ b/package_python_function/packager.py
@@ -68,6 +68,7 @@ def zip_dir(path: Path) -> None:
                         )
                         zinfo.date_time = date_time()
                         zinfo.external_attr = 0o644 << 16
+                        zinfo.compress_type = zipfile.ZIP_DEFLATED
                         self._uncompressed_bytes += item.stat().st_size
                         with (
                             open(item, "rb") as src,