Dropper and dispenser not powered correctly by redstone torch

When one puts a redstone torch on a block in such a way that it is directly above a dropper or dispenser (see screenshot) and turns that torch off an on several times (via redstone or via the lever in the screenshot), the dropper/dispenser will not fire as it should.

What I expected to happen was: dropper/dispenser fires at each switching from off to on and at no switching from on to off.

What actually happened was: dropper/dispenser fires the first time the torch is switched, even if it's from on to off, and then doesn't react at all anymore. After removing the dropper and putting it back, it will again fire once.

Steps to Reproduce:
1. Build the stuff from the screenshot; put the dropper last.
2. Put several items in the dropper.
3. Switch the leve a few times.

Additional remarks:

• When the torch is beside the dropper instead of above it, there seems to be no problem.

• I also tested tnt and a redstone lamp instead of a dropper; this worked properly.

• The following also works properly: build the construction from the screenshot, but leave away the lever and put the redstone torch last. Then the dropper will fire in the moment you put the torch.