new.env does not recognize parents from subclasses of "environment"

Dear Developers,

A lot has been changed in the R12.0 with respect to behavior of "environment"
subclasses.  Many thanks for that.

One small irregularity, though; new.env does not allow the parent to be from S4
subclass.

setClass("myenv", contains="environment")

[1] "myenv"

new.env(parent=new("myenv"))

Error in new.env(parent = new("myenv")) : 'enclos' must be an environment

I wonder if this is a "planed" behavior.

The use of .xData  slot obviously works:

new.env(parent=new("myenv")@.xData)

<environment: 063bb9e8>

Thanks,
Vitaly.