Unfortunately, this got messed up in the 9.1.3 release. It should be MappedSuperclass.
The easiest solution is to use 9.1.2 until 9.2 is released (release candidate is out now if you want to try it here: Concrete CMS 9.2.0RC2 Now Available!
Unfortunately, this got messed up in the 9.1.3 release. It should be MappedSuperclass.
The easiest solution is to use 9.1.2 until 9.2 is released (release candidate is out now if you want to try it here: Concrete CMS 9.2.0RC2 Now Available!