[NTG-context] colon in caption

Hi all, I have the question how to put a (pure) colon into a figure or table caption. \let\floatcaptionsuffix=: \placefigure[fig:cow]{cow}{\externalfigure[cow]} produces: Figure 1.: cow What I want is: Figure 1: cow i.e. the colon without the additionally dot. Does somebody know a solution for this simple problem? With many thanks for any hint, Albrecht