Vscode plugin does not work in theia

Hello. I have vscode plugin with custom editor. Custom editor has iframe in it. Iframe loads local resources from this plugin. Plugin works fine in vscode but it does not work in theia. I get errors like:
GET http://794a321d-e320-4e7d-ae32-fc4225828d18.webview.localhost:3000/webview/theia-resource/path/to/plugin/myCode.js net::ERR_ABORTED 404 (Not Found)

Is this a bug or am i doing something wrong?