The Bloomington Drosophila Stock Center has identified l(3)95EFb1807 (FBal0150377) and l(3)95EFb2328 (FBal0150376) as alleles of the mask gene.  Both mutations are homozygous lethal and fail to complement Df(3R)crb87-4 (RRID:BDSC_2362) and PBac{IT.GAL4}mask0380-G4 (RRID:BDSC_62817). Whole genome sequencing reveals the following changes in the mask gene:
l(3)95EFb1807 = mask1807, mask-PA, PB, and PE Q995stop (CAG->TAG); mask-PC Q1007stop; mask-PD Q630stop; mask-PF Q617stop
l(3)95EFb2328 = mask2328, G at  3R:24240106  (r6) is deleted resulting in a frameshift following R1554 (in mask-PA) with 11 aa (AEKTWLLTHHS) of frameshifted protein translated before hitting a stop codon. The protein is truncated less than halfway through.