diff --git a/main.js b/main.js
index 69a1a3b..8e8b988 100644
--- a/main.js
+++ b/main.js
@@ -251,7 +251,7 @@ function createWindow(env) {
         try {
             let da3 = fs.readFileSync(path.join(env.paths.ffmpeg, 'virtual_device.wvd'), { encoding: "binary" })
             let buf = Buffer.from(da3, 'binary')
-            .FS.writeFile("/device.wvd", buf, { encoding: "binary" });
+            pyodide.FS.writeFile("/device.wvd", buf, { encoding: "binary" });
         } catch (e) {
             win.webContents.openDevTools();
             setTimeout(console.log, 1000, 'no virtual device file detected in binaries directory : please consider donation on\nhttps://donorbox.org/youtube-dl-gui')