diff --git a/package-lock.json b/package-lock.json
index 95d18bb..e68a037 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -525,6 +525,11 @@
         "minimalistic-assert": "^1.0.0"
       }
     },
+    "detect-node": {
+      "version": "2.0.4",
+      "resolved": "https://registry.npmjs.org/detect-node/-/detect-node-2.0.4.tgz",
+      "integrity": "sha512-ZIzRpLJrOj7jjP2miAtgqIfmzbxa4ZOr5jJc601zklsfEx9oTzmmj2nVpIPRpNlRTIh8lc1kyViIY7BWSGNmKw=="
+    },
     "dfa": {
       "version": "1.2.0",
       "resolved": "https://registry.npmjs.org/dfa/-/dfa-1.2.0.tgz",
diff --git a/package.json b/package.json
index 89c8bb8..4d3a5d8 100644
--- a/package.json
+++ b/package.json
@@ -36,6 +36,7 @@
     "dist/main.js"
   ],
   "dependencies": {
+    "detect-node": "^2.0.4",
     "pdfkit": "git+https://github.com/Xmader/pdfkit.git",
     "svg-to-pdfkit": "^0.1.8",
     "webmscore": "^0.10.4"
diff --git a/src/mscore.ts b/src/mscore.ts
index e9efcfa..2f26308 100644
--- a/src/mscore.ts
+++ b/src/mscore.ts
@@ -3,6 +3,7 @@
 import { fetchMscz } from './mscz'
 import { fetchData } from './utils'
 import { ScoreInfo } from './scoreinfo'
+import isNodeJs from 'detect-node'
 
 const WEBMSCORE_URL = 'https://cdn.jsdelivr.net/npm/webmscore@0.10/webmscore.js'
 
@@ -16,8 +17,8 @@ const SOUND_FONT_LOADED = Symbol('SoundFont loaded')
 export type WebMscore = import('webmscore').default
 export type WebMscoreConstr = typeof import('webmscore').default
 
-const initMscore = async (w?: Window): Promise<WebMscoreConstr> => {
-  if (w !== undefined) { // attached to a page
+const initMscore = async (w: Window): Promise<WebMscoreConstr> => {
+  if (!isNodeJs) { // attached to a page
     if (!w['WebMscore']) {
       // init webmscore (https://github.com/LibreScore/webmscore)
       const script = w.document.createElement('script')
@@ -32,11 +33,11 @@ const initMscore = async (w?: Window): Promise<WebMscoreConstr> => {
 }
 
 let fonts: Promise<Uint8Array[]> | undefined
-const initFonts = (nodeJs: boolean) => {
+const initFonts = () => {
   // load CJK fonts
   // CJK (East Asian) characters will be rendered as "tofu" if there is no font
   if (!fonts) {
-    if (nodeJs) {
+    if (isNodeJs) {
       // module.exports.CN = ..., module.exports.KR = ...
       const FONTS = Object.values(require('@librescore/fonts'))
 
@@ -65,8 +66,8 @@ export const loadSoundFont = (score: WebMscore): Promise<void> => {
 }
 
 export const loadMscore = async (scoreinfo: ScoreInfo, w?: Window): Promise<WebMscore> => {
-  initFonts(w === undefined)
-  const WebMscore = await initMscore(w)
+  initFonts()
+  const WebMscore = await initMscore(w!)
 
   // parse mscz data
   const data = new Uint8Array(