[NTG-context] Broken Nightly 2012.07.04 23:48 - \xRightarrow

Hi, Some math symbols seem to be failing with the latest nightly build. Minimal example: \starttext \section{blah} AAAAA $a \xRightarrow b$ BBBBB. \stoptext I see this in the output: ConTeXt ver: 2012.07.04 23:48 MKIV fmt: 2012.7.6 int: english/english system > tex > error on line 3 in file demo.context: Undefined control sequence ... ... ... ... \math_arrows_construct_single ...s \p_mathspacing \endcsname \p_mathspacing ... \math_arrows_handle_finalize ...{#7}{#1}{#4}{}{#8} }\fi \else \ifsecondargume... <to be read again> b l.3 AAAAA $a \xRightarrow b $ BBBBB. ! Undefined control sequence. system > tex > error on line 3 in file demo.context: Undefined control sequence ...