diff --git a/ChangeLog b/ChangeLog
index 599144ebbe..3f0f4f3bc8 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Wed Jul  6 21:23:38 2011  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
+
+	* cont.c (fiber_machine_stack_alloc): use MAP_STACK if it's provided.
+
 Wed Jul  6 21:22:16 2011  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
 
 	* cont.c (fiber_machine_stack_alloc): use MAP_FAILED instead of -1.
diff --git a/cont.c b/cont.c
index db4d93bca5..e46f52ccf0 100644
--- a/cont.c
+++ b/cont.c
@@ -515,7 +515,14 @@ fiber_entry(void *arg)
     fiber_set_stack_location();
     rb_fiber_start();
 }
+#else /* _WIN32 */
+
+#ifdef MAP_STACK
+#define FIBER_STACK_FLAGS (MAP_PRIVATE | MAP_ANON | MAP_STACK)
 #else
+#define FIBER_STACK_FLAGS (MAP_PRIVATE | MAP_ANON)
+#endif
+
 static VALUE*
 fiber_machine_stack_alloc(size_t size)
 {
@@ -536,7 +543,7 @@ fiber_machine_stack_alloc(size_t size)
     else {
 	void *page;
 	STACK_GROW_DIR_DETECTION;
-	ptr = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0);
+	ptr = mmap(NULL, size, PROT_READ | PROT_WRITE, FIBER_STACK_FLAGS, -1, 0);
 	if (ptr == MAP_FAILED) {
 	    rb_raise(rb_eFiberError, "can't alloc machine stack to fiber");
 	}