diff --git a/.github/scripts/fix-mtime b/.github/scripts/fix-mtime
index 5c8983e..401506e 100755
--- a/.github/scripts/fix-mtime
+++ b/.github/scripts/fix-mtime
@@ -1,7 +1,31 @@
-#!/usr/bin/env sh
+#!/bin/sh -e
 
-git ls-tree -r --name-only HEAD | while read filename; do
-  unixtime=$(git log -1 --format="%at" -- "${filename}")
-  touchtime=$(date -d @$unixtime +'%Y%m%d%H%M.%S')
-  touch -t ${touchtime} "${filename}"
+OS=${OS:-$(uname)}
+
+if [ "$OS" = 'Darwin' ]; then
+	get_touch_time() {
+		date -r "${unixtime}" +'%Y%m%d%H%M.%S'
+	}
+else
+	# default Linux
+	get_touch_time() {
+		date -d @"${unixtime}" +'%Y%m%d%H%M.%S'
+	}
+fi
+
+# all git files
+git ls-tree -r --name-only HEAD >.git_ls-tree_r_name-only_HEAD
+
+# modified git files
+git diff --name-only >.git_diff_name-only
+
+# minus https://stackoverflow.com/questions/1370996/minus-operation-on-two-files-using-linux-commands
+# only restore files not modified
+comm -2 -3 .git_ls-tree_r_name-only_HEAD .git_diff_name-only | while read -r filename; do
+	unixtime=$(git log -1 --format="%at" -- "${filename}")
+	touchtime=$(get_touch_time)
+	echo "${touchtime}" "${filename}"
+	touch -t "${touchtime}" "${filename}"
 done
+
+rm .git_ls-tree_r_name-only_HEAD .git_diff_name-only