What I expected to happen was...:
The item frame and the item in it should be knocked down to the floor.

What actually happened was...:
Both the item frame and the item in it clip upwards and end up on the ceiling.

Steps to Reproduce: (screenshots illustrate each step)
1. Have an item frame one block under the ceiling.
2. Knock down the item or the item frame.
3. Check for the items on top of the ceiling.