Form 5558 - Incorrect Plan Name and Plan Number

The employer sponsors 2 retirement plans - one is a regular 401k and the other is a 457 Plan for which has no 5500 filing requirement - when filing the 5558 to extend the 12/31/2018 filing due 7/31/2019, the 401k was intended to be extended but the 457's plan name and number were used by mistake - is fixing this as simple as sending correspondence to the IRS in advance of them sending any late filing notice to bring the issue to their attention?    On the IRS website, it addresses getting a late filing notice and at that point realizing incorrect incorrect info was entered on the 5558 and just responding to that late notice indicating your error... I'm figuring, it's always best to get in front of the issue as soon as we know about it and not wait for a late notice from IRS...    and when / if we do get a late notice, being able to point to correspondence that brings the issue to their attention... anyone's thoughts would be greatly appreciated