Is there a way to tell TypeScript that an external type has additional properties?

I’m using an external JS library in which additional properties are defined on a class prototype using Object.defineProperties(ClassName.prototype, ...).

Typescript, for some reason, doesn’t recognize these properties (properties that defined in the constructor are recognized just fine).

This library has very poor typescript definition (many classes and properties are missing), so I can’t use it.

Is there a way to tell TS that these properties are actually exist on this specific class?