baleful polymorph used on undead

[Brekke]

The druid in our wants to know if baleful polymorph can be used on undead. The spell save is a fort and most undead don't have forts so she is wondering if that means the spell automatically works?

 

[Malachi of Kossuth]

Undead are immune to all spells that require a fortitude save unless they affect OBJECTS also.

 

[Brekke]

Thank you