diff --git a/script/update/project/release b/script/update/project/release
index e7973537..ee41c916 100755
--- a/script/update/project/release
+++ b/script/update/project/release
@@ -232,11 +232,11 @@ mktarball()
 	[ "${2%/*}" = "${2}" ] || x_ mkdir -p "${2%/*}"
 	if [ "${tar_implementation% *}" = "tar (GNU tar)" ]; then
 		tar --sort=name --owner=root:0 --group=root:0 \
-		    --mtime="UTC 2023-10-14" -c "${1}" | xz -T0 -9e > "${2}" || \
+		    --mtime="UTC 2023-10-14" -c "${1}" > "${2}" || \
 		    err "mktarball 1, ${1}"
 	else
 		# TODO: reproducible tarballs on non-GNU systems
-		tar -c "${1}" | xz -T0 -9e > "${2}" || err "mktarball 2, ${1}"
+		tar -c "${1}" > "${2}" || err "mktarball 2, ${1}"
 	fi
 	(
 	[ "${2%/*}" != "${2}" ] && x_ cd "${2%/*}"