How can I validate request body if it's a union type?

[gtamas]

I have this situation:

class A {
// some validators
}

class B {
// some validators
}

And in controller:

someMethod(
    @Param('id') id: string,
    @Body() params: A | B,
  ): Promise<SomeResult>

This doesn't work. None of the class validators get executed, I guess that's because the body is not a class, but a union of classes.

Is there any way to make this work? I want the body to be validated either as class A or B.