diff --git a/ChangeLog b/ChangeLog
index fdac0ae480..8e97b73f48 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+Wed Apr  1 13:46:20 2009  Yukihiro Matsumoto  <matz@ruby-lang.org>
+
+	* thread.c (rb_thread_fd_select): new function to call select
+	  using rb_fdset_t.
+
+	* io.c (select_internal): use rb_thread_fd_select instead of
+	  rb_thread_select.  based on the patch from Kengo Matsuyama.
+	  [ruby-dev:38221]
+
 Wed Apr  1 13:16:19 2009  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* process.c (rb_f_sleep): RDoc disambiguation.  [ruby-talk:332632]
diff --git a/include/ruby/intern.h b/include/ruby/intern.h
index 617c11808e..49a27fc74a 100644
--- a/include/ruby/intern.h
+++ b/include/ruby/intern.h
@@ -244,6 +244,7 @@ typedef fd_set rb_fdset_t;
 #define rb_fd_clr(n, f)	FD_CLR(n, f)
 #define rb_fd_isset(n, f) FD_ISSET(n, f)
 #define rb_fd_copy(d, s, n) (*(d) = *(s))
+#define rb_fd_resize(n, f)	(void)(f)
 #define rb_fd_ptr(f)	(f)
 #define rb_fd_init(f)	FD_ZERO(f)
 #define rb_fd_term(f)	(void)(f)
@@ -327,6 +328,7 @@ VALUE rb_thread_create(VALUE (*)(ANYARGS), void*);
 void rb_thread_signal_raise(void *, int);
 void rb_thread_signal_exit(void *);
 int rb_thread_select(int, fd_set *, fd_set *, fd_set *, struct timeval *);
+int rb_thread_fd_select(int, rb_fdset_t *, rb_fdset_t *, rb_fdset_t *, struct timeval *);
 void rb_thread_wait_for(struct timeval);
 VALUE rb_thread_current(void);
 VALUE rb_thread_main(void);
diff --git a/io.c b/io.c
index 38570eb065..ddfb5e0f43 100644
--- a/io.c
+++ b/io.c
@@ -6635,7 +6635,7 @@ static VALUE
 select_internal(VALUE read, VALUE write, VALUE except, struct timeval *tp, rb_fdset_t *fds)
 {
     VALUE res, list;
-    fd_set *rp, *wp, *ep;
+    rb_fdset_t *rp, *wp, *ep;
     rb_io_t *fptr;
     long i;
     int max = 0, n;
@@ -6658,7 +6658,7 @@ select_internal(VALUE read, VALUE write, VALUE except, struct timeval *tp, rb_fd
 	    timerec.tv_sec = timerec.tv_usec = 0;
 	    tp = &timerec;
 	}
-	rp = rb_fd_ptr(&fds[0]);
+	rp = &fds[0];
     }
     else
 	rp = 0;
@@ -6671,7 +6671,7 @@ select_internal(VALUE read, VALUE write, VALUE except, struct timeval *tp, rb_fd
 	    rb_fd_set(fptr->fd, &fds[1]);
 	    if (max < fptr->fd) max = fptr->fd;
 	}
-	wp = rb_fd_ptr(&fds[1]);
+	wp = &fds[1];
     }
     else
 	wp = 0;
@@ -6690,7 +6690,7 @@ select_internal(VALUE read, VALUE write, VALUE except, struct timeval *tp, rb_fd
                 if (max < fptr->fd) max = fptr->fd;
             }
 	}
-	ep = rb_fd_ptr(&fds[2]);
+	ep = &fds[2];
     }
     else {
 	ep = 0;
@@ -6698,7 +6698,7 @@ select_internal(VALUE read, VALUE write, VALUE except, struct timeval *tp, rb_fd
 
     max++;
 
-    n = rb_thread_select(max, rp, wp, ep, tp);
+    n = rb_thread_fd_select(max, rp, wp, ep, tp);
     if (n < 0) {
 	rb_sys_fail(0);
     }
diff --git a/thread.c b/thread.c
index 3627811bfb..dacd85b34f 100644
--- a/thread.c
+++ b/thread.c
@@ -2490,6 +2490,37 @@ rb_thread_select(int max, fd_set * read, fd_set * write, fd_set * except,
 }
 
 
+int
+rb_thread_fd_select(int max, rb_fdset_t * read, rb_fdset_t * write, rb_fdset_t * except,
+		    struct timeval *timeout)
+{
+    fd_set *r = NULL, *w = NULL, *e = NULL;
+
+    if (!read && !write && !except) {
+	if (!timeout) {
+	    rb_thread_sleep_forever();
+	    return 0;
+	}
+	rb_thread_wait_for(*timeout);
+	return 0;
+    }
+
+    if (read) {
+        rb_fd_resize(max - 1, read);
+        r = rb_fd_ptr(read);
+    }
+    if (write) {
+        rb_fd_resize(max - 1, write);
+        w = rb_fd_ptr(write);
+    }
+    if (except) {
+        rb_fd_resize(max - 1, except);
+        e = rb_fd_ptr(except);
+    }
+    return do_select(max, r, w, e, timeout);
+}
+
+
 /*
  * for GC
  */