Index: /trunk/source/lisp-kernel/x86-exceptions.c
===================================================================
--- /trunk/source/lisp-kernel/x86-exceptions.c	(revision 15471)
+++ /trunk/source/lisp-kernel/x86-exceptions.c	(revision 15472)
@@ -1024,4 +1024,10 @@
     save_vsp = xpGPR(xp,Isp),
     save_fp = xpGPR(xp,Ifp);
+#ifdef DARWIN /* bug in <= 10.5 */
+  void decode_vector_fp_exception(siginfo_t *, uint32_t);
+
+  decode_vector_fp_exception(info, (uint32_t)(UC_MCONTEXT(xp)->__fs.__fpu_mxcsr));
+#endif
+
 #ifdef WINDOWS
   code = info->ExceptionCode;
@@ -1099,4 +1105,6 @@
     }
   }
+  /* Nothing enabled and set in the mxcsr, assume integer /0 */
+  info->si_code = FPE_INTDIV;
 }