Namespace lost after update

[Federico Cavalieri]

In the following query the namespace binding on d,e,f are lost after the delete node operation evaluation.
I believe the problem is in detach.

variable $x:=<a><a1 xmlns="http://aaa.com" c1="d1"><d xmlns="http://ddd.com"/><e:e xmlns:e="http://eee"><f:f xmlns:f="f">g</f:f></e:e></a1></a>;
variable $z:=$x/*;
delete node $x/*;
$z

The query outputs:
<a1 xmlns="http://aaa.com" c1="d1"><d/><e:e><f:f>g</f:f></e:e></a1>

The query should output:
<a1 xmlns="http://aaa.com" c1="d1"><d xmlns="http://ddd.com"/><e:e xmlns:e="http://eee"><f:f xmlns:f="f">g</f:f></e:e></a1>