Eldritch Smite: Can you decide whether the enemy goes prone or do they always go prone?

Once per turn when you hit a creature with your pact weapon, you can expend a warlock spell slot to deal an extra 1d8 force damage to the target, plus another 1d8 per level of the spell slot, and you can knock the target prone if it is Huge or smaller.

Since it says "can knock the target prone." I assumed it was optional, (though you wouldn’t have much reason not to if in melee, within 5 ft.)