From the Wikipedia page for "Self-serving bias," emphasis mine:

Locus of control is one of the main influences of attribution style. Individuals with an internal locus of control believe that they have personal control over situations and that their actions matter. Those with an external locus of control believe that outside forces, chance, and luck determine situations and that their actions cannot change anything. Individuals with an external locus of control are more likely to exhibit a self-serving bias following failure than those with an internal locus of control. The difference in attribution style between individuals with internal and external loci of control, however, is not as marked in successful outcomes, as individuals with both types attribution style have less need to defend their self-images in success. Airplane pilots with an internal locus of control were likely to exhibit a self-serving bias in regard to their skill and levels of safety.