diff --git a/ChangeLog b/ChangeLog
index fca5dae5c7..408893e112 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Sat Mar 16 03:36:56 2013  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
+
+	* thread.c (ruby_kill): release GVL while waiting signal delivered.
+
 Tue Mar 19 19:50:48 2013  NAKAMURA Usaku  <usa@ruby-lang.org>
 
 	* ruby_kill (internal.h, thread.c): use rb_pid_t instead of pid_t.
diff --git a/thread.c b/thread.c
index 37e805358a..9f723d0d64 100644
--- a/thread.c
+++ b/thread.c
@@ -5211,10 +5211,12 @@ ruby_kill(rb_pid_t pid, int sig)
     rb_vm_t *vm = GET_VM();
 
     if ((th == vm->main_thread) && (pid == getpid())) {
+	GVL_UNLOCK_BEGIN();
 	native_mutex_lock(&th->interrupt_lock);
 	err = kill(pid, sig);
 	native_cond_wait(&th->interrupt_cond, &th->interrupt_lock);
 	native_mutex_unlock(&th->interrupt_lock);
+	GVL_UNLOCK_END();
     } else {
 	err = kill(pid, sig);
     }