diff --git a/package.json b/package.json
index 87cb77f..ea86c2f 100644
--- a/package.json
+++ b/package.json
@@ -3,6 +3,7 @@
   "version": "1.1.1",
   "description": "A fast, lightweight, zero-dependency library to translate between Time Zones and UTC with native Intl.DateTimeFormat in ~100 LoC. For Node.js & Browsers.",
   "main": "xtz.js",
+  "files": ["xtz.js", "tolocalisostring.js"],
   "scripts": {
     "test": "node ./test.js",
     "build": "uglifyjs ./xtz.js > ./xtz.min.js ; gzip -k -f ./xtz.min.js"