diff --git a/ChangeLog b/ChangeLog
index 8e1601f709..976cc42d04 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Wed Jul  6 21:21:05 2011  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
+
+	* cont.c (fiber_machine_stack_alloc): remove unnecessary cast.
+
 Wed Jul  6 18:10:13 2011  Shota Fukumori  <sorah@tubusu.net>
 
 	* test/cgi/test_cgi_header.rb(test_cgi_header_nph): Adding space after
diff --git a/cont.c b/cont.c
index aa144ce619..e260a40053 100644
--- a/cont.c
+++ b/cont.c
@@ -536,7 +536,7 @@ fiber_machine_stack_alloc(size_t size)
     else {
 	void *page;
 	STACK_GROW_DIR_DETECTION;
-	ptr = (VALUE*)mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0);
+	ptr = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0);
 	if (ptr == (VALUE*)(SIGNED_VALUE)-1) {
 	    rb_raise(rb_eFiberError, "can't alloc machine stack to fiber");
 	}