Does the Geas spell end if Lamia die?

@ChrisPerkinsDnD if a lamia casts geas on a pc, but the party kills the lamia, does the geas spell end? Or does it go until PC finishes task

— Andrew Cherluck (@archerluck) April 12, 2016

The spell doesn't end when the lamia dies. https://t.co/UHwYq1eL4p

— Christopher Perkins (@ChrisPerkinsDnD) April 12, 2016