Can't sprint when inside blocks in spectator mode

Put the summary of the bug you're having here

What I expected to happen was...:
That I would start "sprinting" while flying through the ground

What actually happened was...:
Nothing happened unless I went back over ground or inside a cave to start sprinting.

Steps to Reproduce:
1. Go in spectator mode
2. Go underground, not in any caves but inside the blocks
3. Try to sprint