Government Code § 21420

If a member retired for industrial disability has made contributions in respect to service rendered in a category of membership other than the category in which he or she was at the time he or she suffered the disability or incurred the disease causing his or her retirement for industrial disability, in addition to the disability retirement allowance to which he or she is otherwise entitled under this article, he or she shall receive an annuity purchased with his or her accumulated normal contributions made in respect to service rendered in the other category of membership.