Index: gc/mach_dep.c
===================================================================
--- gc/mach_dep.c	(revision 6723)
+++ gc/mach_dep.c	(working copy)
@@ -159,7 +159,7 @@
 # undef HAVE_PUSH_REGS
 #endif
 
-#if !defined(HAVE_PUSH_REGS) && defined(UNIX_LIKE)
+#if !defined(HAVE_PUSH_REGS) && defined(UNIX_LIKE) && !defined(DARWIN)
 # include <ucontext.h>
 #endif