diff --git a/package.json b/package.json
index ac4b8d508..0ef620153 100644
--- a/package.json
+++ b/package.json
@@ -10,6 +10,7 @@
     "@babel/eslint-plugin": "^7.12.1",
     "@babel/plugin-proposal-class-properties": "^7.10.1",
     "@babel/plugin-proposal-private-methods": "^7.12.1",
+    "@babel/plugin-transform-modules-umd": "^7.12.1",
     "@babel/preset-env": "^7.12.7",
     "@uupaa/dynamic-import-polyfill": "^1.0.2",
     "autoprefixer": "^9.8.6",