Execute command error messages

In this beta, the execute command is no longer allowing executed entities to summon things.

 

Here is an example of a command which I use all the time which has now broke.

 

/execute @e[name=Vampire] ~~~ detect ~~~ air 0 summon skeleton ~~~

 

This command should make the vampire named mob summon a skeleton, however in this update it comes up with the error "unable to summon object as Vampire"

 

Please fix this