Peter Nimmervoll before this fix, Weld wouldn't work with signed packaged at all and the fix only applies if Class<?>.getSigners() != null.
E.g. what Martin says means that the solution isn't perfect for signed packages with package private members - this you couldn't do before either.

Are you sure this is causing your problems? If so, could you share more details about your use-case and when does the security manager come into play?