Daily Punch 3-25-20 Proficient Ambush feat for DnD 5e

You don’t add proficiency to damage OR DO YOU?

Proficient Ambush

Prerequisite: sneak attack

Train long enough and you learn how to do a few things.  Gain the following:

• Increase your Dexterity by 1, to a maximum of 20.
• Once per turn, when you hit a target and apply sneak attack you can add your proficiency to the damage dealt.

Thoughts?