Index: /trunk/ccl/compiler/X86/X8664/x8664-backend.lisp
===================================================================
--- /trunk/ccl/compiler/X86/X8664/x8664-backend.lisp	(revision 4970)
+++ /trunk/ccl/compiler/X86/X8664/x8664-backend.lisp	(revision 4971)
@@ -179,4 +179,5 @@
 		:p2-template-hash-name '*x8664-vinsn-templates*
 		:p2-compile 'x862-compile
+                :platform-syscall-mask (logior platform-os-darwin platform-cpu-x86 platform-word-size-64) 
 		:target-specific-features
 		'(:x8664 :x86-target :darwin-target :darwinx86-target :x8664-target
@@ -195,5 +196,6 @@
                 :define-callback 'define-x8664-callback
                 :defcallback-body 'defcallback-body-x8664
-                :lisp-context-register x8664::fs
+                ;; Overload %gs until Apple straightens things out.
+                :lisp-context-register x8664::gs
                 ))