ERROR TypeError: Class constructor Subscriber cannot be invoked without 'new'

[agonhasani]

Getting this error when trying to use the library in an Angular 8 project.

ERROR TypeError: Class constructor Subscriber cannot be invoked without 'new'

This happens only when the target in tsconfig.ts is set to es2015.

A workaround is to set the target to es5 but then this disables differential loading in Angular.