[NTG-context] \overrightarrow{AB} gives under rightarrow

Dear all. The following short sample gives a under right arrow instead of over right arrow. Would you please check it? \starttext $\overrightarrow{AB}$ \stoptext Thanks. Best regards, Dalyoung ConTeXt ver: 2012.10.06 15:31 MKIV fmt: 2012.10.8 int: english/english