Well, yes, the *doctrine* of materialism is defined by the belief in objective reality. The objective reality itself is indifferent to our belief in it or otherwise.
Paul Mattick wrote a good piece on Marxism and the New Physics where he tries to disentangle historical materialism from philosophical materialism (thereby excusing Marxism from any damage Quantum Physics did to the latter). Mattick says that the postulate of historical materialism is only that men in transforming their conditions of existence transform themselves. That postulate, in itself, is not affected by the philosophical question raised by quantum physics. Tacking in the opposite direction to Lenin, Mattick is saying that there is no requirement on Marxists to defend philosophical materialism. -- James Heartfield