[NTG-context] Degree sign half-works

Hi all. The following, when run through live.contextgarden.net (and my own installation), produces odd results: %Input is utf8 (Unicode) \enableregime[utf] \useencoding[uc] %MathML is processed directly \useXMLfilter[utf] \usemodule[mathml] \starttext Test normal text: 180° Test MathML: \startXMLdata <math display="block" id="gincp74b"> <mrow> <mn>108</mn><mo>°</mo> </mrow> </math>\stopXMLdata \stoptext When the degree sign appears in normal text it works fine, when it appears in MathML it comes out as $^$. I have been searching in the base files but can't see the hook. Can anyone point me in the right direction to fix this? Thanks. Duncan