A composition comprising a non-miscible blend of, as a major component, a linear alternating polymer of carbon monoxide and at least one ethylenically unsaturated hydrocarbon and lesser amounts of a maleated, partially hydrogenated block copolymer, said block copolymer having at least one at least predominantly polymerized vinyl aromatic compound block and at least one at least predominantly aliphatic polymerized conjugated alkadiene block, and ceramic fiber reinforcement.