The signature of Doclet.getSupportedOptions uses a wildcard in the return type.

Set<? extends Doclet.Option> getSupportedOptions()

There is an overriding method in StandardDoclet, but it incorrectly omits the wildcard, this providing a more restrictive return type.

public Set<Doclet.Option> getSupportedOptions()

Although this will be an API change, it will not affect existing clients or any subtypes.