Maybe I found it, here's the patch: $ cd ccl/level-0 $ diff l0-numbers.lisp.~1.31.~ l0-numbers.lisp 1785c1785 < (%multiply 42871 (dpb (ldb (byte 15 0) high) --- > (%multiply 48271 (dpb (ldb (byte 15 0) high) -- Bernd