Amethyst Clusters not working with Silk Touch Enchant

Put the summary of the bug you're having here

What I expected to happen was...:
The amethyst cluster to drop itself

What actually happened was...:
The cluster was successfully broken but no item was dropped

Steps to Reproduce:
1. Enchant a Iron Pick or Higher with the Silk Touch Enchantment
2. Break an amethyst cluster with the pickaxe