Unchecked cast from X to generic type that extends X

I've been tasked with removing as many @SupressWarnings as possible in our codebase, and I'm not sure how to get around this particular issue.

I have this external method that returns a Serializable object, and a generic type T extends Serializable that I would like to cast the object to.

Here is a simplified version of the code:

class A <T extends Serializable> {

    public T someMethod() {
        Serializable result = someExternalMethod(...);
        T convertedObject = (T) result; // produces unchecked cast warning

        return convertedObject;
    }
}

Is it possible to perform this conversion without producing an unchecked cast warning (assuming the external method cannot be changed)?

This is Java 8.

To extend the answer of ferpel you can pass the type as a parameter

    class A <T extends Serializable> {

        public T someMethod(Class<T> type) {
            Serializable result = someExternalMethod(...);
            return type.cast(result);
        }
    }