Hopper + Detector-Rail = Senseless

Its not a real "bug" but theres no use of die combination.

I want to empty a chest in a minecart and check the signal with a redstone comperator and a detector rail.

right under the detector rail, there is a hopper. but the signal from the detector rail disables the hopper, so there is no chance to empty the chest.

it makes the combination detector rail + item hopper senseless.

to reproduce: simply place a minecart with chest and items in it on top of a detector rail and under the detector rail, place a hopper.

thanks!