I am getting this error when I tried to build for production. ng build --prod --aot
 "angularfire2": "^5.0.0-rc.6",
 "@angular/compiler-cli": "^5.2.0",
"@angular/cli": "~1.7.0",
WARNING in ./src/app/app.module.ngfactory.js
110:18734-18740 "export 'ɵa' (imported as 'i47') was not found in 'angularfire2/firestore'
Works well with development ng serve.