Early goals by teenage striker Callum Ball and Paul Green earned Derby a second successive win over the Christmas period as they beat West Ham.
Ball, 19, struck his second senior goal from the edge of the area in the second minute and Green headed his first goal in over a year eight minutes later.
Hammers striker Frank Nouble replied with a rasping drive before the break.
But Derby have now won three of their last four league games and are within two points of the play-offs.
West Ham, depleted by injuries and suspensions, have won only one of their last five league games. They could have gone joint top of the Championship table following Southampton's Friday night defeat by Bristol City.