Issue for morphing Units.

[Thobewill]

I am trying to give Hydralisks the Lurker Aspect ability. I add the ability to the unit, but when I go to add it to the command card, Lurker Aspect does not show up in the dropdown box. I am using blizzard's own Lurker Aspect ability, but can't seem to add it to the Hydralisks. Anyone know how to fix this?