diff --git a/vm/os-macosx-x86.h b/vm/os-macosx-x86.h
index fa40595027..2daf2cbc94 100644
--- a/vm/os-macosx-x86.h
+++ b/vm/os-macosx-x86.h
@@ -1,7 +1,7 @@
 #define SIGSEGV_EXC_STATE_TYPE i386_exception_state_t
 #define SIGSEGV_EXC_STATE_FLAVOR i386_EXCEPTION_STATE
 #define SIGSEGV_EXC_STATE_COUNT i386_EXCEPTION_STATE_COUNT
-#define SIGSEGV_EXC_STATE_FAULT(exc_state) (exc_state).dar
+#define SIGSEGV_EXC_STATE_FAULT(exc_state) (exc_state).faultvaddr
 #define SIGSEGV_THREAD_STATE_TYPE i386_thread_state_t
 #define SIGSEGV_THREAD_STATE_FLAVOR i386_THREAD_STATE
 #define SIGSEGV_THREAD_STATE_COUNT i386_THREAD_STATE_COUNT
@@ -18,6 +18,6 @@ INLINE unsigned long fix_stack_ptr(unsigned long sp)
 
 INLINE void pass_arg0(SIGSEGV_THREAD_STATE_TYPE *thr_state, CELL arg)
 {
-	put(SIGSEGV_STACK_POINTER(thr_state),arg);
-	SIGSEGV_STACK_POINTER(thr_state) -= CELLS;
+	*(CELL *)thr_state->esp = arg;
+	thr_state->esp -= CELLS;
 }