This paper addresses the vicious remarks in one of Karl Marx’s letters, which have been frequently used to denounce Marx as a committed anti-Semite. In contrast, the paper points out, firstly, that the letter in question combines two racisms (directed against Jewishness and black-ness). Secondly, it is emphasized that Marx always took a principally emancipatory position. He did not however subject the two racisms to critical scrutiny. As a result, he neither conceptually penetrated nor intellectually superated the codes of anti-Semitism and colonial racism current in his day, but rather reproduced them, at least in part, as is, thirdly, documented. Fourthly and finally, it is concluded that this analytic deficit has proved an obstacle for the development of a Marxist theory of racism and has a negative impact on Marxist discussions of racism to this day.