The rupee closed marginally weaker on Wednesday, as importers bought dollars to cover payments, dealers said. The rupee, which traded at 138.85/95 against the dollar during the day, ended at 138.90/dollar, compared with the previous closing of 138.86. In the open market, the rupee weakened slightly to close at 139.20 against the greenback. It closed at 139 to the dollar in the previous session.