XP Orb shadows

When you look straight down only the XP orb shadows are visible, not the orbs themselves.

Steps to Reproduce:
1. Get XP Orbs
2. Look down

Note: I am running OptiFine, maybe it is an OptiFine bug but I thought it was a vanilla bug.

https://www.youtube.com/watch?v=T_ja5DD1auM&feature=youtu.be