A bispecific bi- or trivalent antibody specifically binding to the two targets which are extracellular domain of human B cell maturation antigen (BCMA) and human CD3ε, wherein the variable domains VL and VH in a light chain and the respective heavy chain are replaced by each other, characterized in comprising a constant domain CL wherein the amino acid at position 124 is substituted independently by lysine (K), arginine (R) or histidine (H) (numbering according to Kabat), and in the respective constant domain CH1 the amino acid at position 147 and the amino acid at position 213 is substituted independently by glutamic acid (E), or aspartic acid (D) (numbering according to EU index of Kabat). Also the manufacture and use of said antibody.