UPDATE: Billboard has changed its initial report that Bob Weir would guest with Phil Lesh & Friends featuring Carlos Santana at this year's Lockn' Festival. The post now says that Weir will be a featured guest on the Saturday of Lockn' 15 as he will appear "in unique artist collaborations" throughout the day. A guest spot with Phil & Friends has not been confirmed contrary to Billboard's initial report.

Bob Weir is the latest addition to the lineup for this year's Lockn' Festival, which takes place in Arrington, Virginia September 10 - 13. Weir is expected to be a featured guest on Saturday, Sept. 12.

Billboard revealed the news which also includes word Mickey Hart has been added to the lineup. Hart will perform with EOTO at the festival as well as participate in a pair of sets billed as "Deep Rhythm Experience" featuring Steve Kimock.

Now all "core four" members of the Grateful Dead are aboard for the festival. Billboard's report also features an image showing harmonica wiz John Popper will be part of Bill Kreutzmann's Billy & The Kids set.

Widespread Panic, Phil Lesh & Friends, The String Cheese Incident, Billy & The Kids and Robert Plant are just a few of the acts set to play Lockn' 2015. The festival will also host tributes to Jefferson Airplane and Joe Cocker as well as sets featuring Panic joined by Jimmy Cliff and Phil Lesh & Friends joined by Santana. Tickets are on sale now via the festival's website.