Designated Beneficiary (Annulment)

Anyone dealt with the issue of how an annulled marriage impacts a beneficiary designation?  Participant designates sister as beneficiary and then gets married.  The spouse becomes the beneficiary under the plans terms (no spousal consent for sister to remain beneficiary).  The marriage is later annulled?  Is the marriage treated as if it didn't happen, which in effect reinstates the sister as beneficiary?  

There have been a few previous discussion threads.  The Search feature might help you.  For example, this one from 2019:

https://benefitslink.com/boards/topic/63887-annulment/

What does the plan say as to when a prior designation become void or ineffective?  Just because there was a marriage doesn't necessarily mean the prior designation is void.  If the participant died during the marriage, the designation would automatically be void because the participant's spouse at the time of his death didn't consent to the designation.   Under the terms of many plans, upon a divorce or, here, an annulment, the old designation might "spring" back in place.