Can't use fork and join with concurrent (orthogonal) regions

Question

Consider state machine definition:

@startuml
state FORK <<fork>>
state JOIN <<join>>
state ORTHO {
  state FIRST
--
  state SECOND
}
[*] --> START
START --> FORK
FORK --> FIRST
FORK --> SECOND
FIRST --> JOIN
SECOND --> JOIN
JOIN --> [*]
@enduml

It does not render with error message: 

But this restriction does not comply with OMG UML 2.5.1 definition of Behavior State Machines (14.2.3.2):

Conversely, an explicit activation occurs when a Region is entered by a Transition  terminating on one of the Region’s contained Vertices. When one Region of an orthogonal State is activated explicitly, this will result in the default activation of all of its orthogonal Regions, unless those Regions are also entered explicitly (multiple orthogonal Regions can be entered explicitly in parallel through Transitions originating from the same fork Pseudostate).

Could you please remove the restriction?