I'm having the following TypeScript class export class Vehicule extends TrackableEntity { vehiculeId: number; constructor() { super(); return super.proxify(this); } } my typescript target in tsconfig.json is configured as es6: "compilerOptions": { "module": "es2015", "moduleResolution": "node", "emitDecoratorMetadata": true, "experimentalDecorators": true, "target": "es6", } At runtime, here in Chrome, the code is failing with: ReferenceError: Cannot access 'Vehicule' before initialization at Module.Vehicule (https://localhost:44338/src-app-components-dispositifsDATI-dispositifsDATI-module.js:10559:100) at Module../src/app/domain/models/VehiculeGpsBoxInfo.ts (https://localhost:44338/src-app-components-dispositifsDATI-dispositifsDATI-module.js:11156:69) at __webpack_require__ (https://localhost:44338/runtime.js:84:30) at Module../src/app/domain/models/Vehicule.ts (https://localhost:44338/src-app-components-dispositifsDATI-dispositifsDATI-module.js:10571:78) at __webpack_require__ (https://localhost:44338/runtime.js:84:30) at Module../src/app/components/dispositifsDATI/mainDATI/listDATI/listDATI.component.ts (https://localhost:44338/src-app-components-dispositifsDATI-dispositifsDATI-module.js:6447:82) at __webpack_require__ (https://localhost:44338/runtime.js:84:30) at Module../src/app/components/dispositifsDATI/index.ts (https://localhost:44338/src-app-components-dispositifsDATI-dispositifsDATI-module.js:3053:95) at __webpack_require__ (https://localhost:44338/runtime.js:84:30) at Module../src/app/components/dispositifsDATI/dispositifsDATI.routes.ts (https://localhost:44338/src-app-components-dispositifsDATI-dispositifsDATI-module.js:2982:64) I needed to change es5 to es6 to solve this other problem. EDIT: The VehiculeGpsBoxInfo.ts file is importing Vehicule like this: import { Vehicule } from "./Vehicule"; EDIT 2: I vould say that this may be webpack related, the way that modules are exported/imported in the genrated modules. EDIT 3: After further research, this seems to have nothing to do with the code shown above. Started a new question about webpack and ES6. Continue reading...