At the end of 20X5, Gernasse carried a deferred tax asset of 50,000 on its share option plan (deduction equal to intrinsic value on exercise, under the tax law in the case). At 31 December 20X6, the share price has fallen below the exercise price: the intrinsic value is nil and no recovery can be anticipated from the information available. Which treatment applies at the 20X6 reporting date?