Does Inspiring Leader work on undead you Control?

Inspiring Leader Says:

choose up to six friendly creatures (which can include yourself) within 30 feet of you can can see or hear you and can understand you. Each creature gains temporary hit point equal to your level + your Charisma modifier.

It seems to me that mindless Skeletons and Zombies would be immune to this sort of buff. However I can’t seem to find any rule for that in 5E.

Is there any reason for Inspiring Leader not to affect your zombies and skeletons?