I am reasonably sure that in mkii this overbar accent was placed correctly, but in mkiv it is shifted to the left. Any ideas on how to fix it?

MWE:

\usemodule[mathml]
\starttext
This \xmlprocessdata{}{<imath><math xmlns='http://www.w3.org/1998/Math/MathML'><mover accent="true"><mi>p</mi><mo>&OverBar;</mo></mover></math></imath>}{} isn't right.
\stoptext