Definition ghost_master sh (a : @G P) p := own p (sh, a) NoneP.

Lemma master_share_join' : forall sh1 sh2 sh v1 v2 p, readable_share sh1 -> readable_share sh2 ->
sepalg.join sh1 sh2 sh ->
ghost_master sh1 v1 p * ghost_master sh2 v2 p = !!(v1 = v2) && ghost_master sh v2 p.