diff --git a/ChangeLog b/ChangeLog
index 2334dbcdb4..029a9711dd 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Mon Feb  5 21:26:56 2007  Koichi Sasada  <ko1@atdot.net>
+
+	* ruby.h: add a prototype of rb_id2str().
+
 Mon Feb  5 21:06:50 2007  Koichi Sasada  <ko1@atdot.net>
 
 	* eval_thread.c, common.mk: remove eval_thread.c.
diff --git a/ruby.h b/ruby.h
index 6c76c70a79..179a1ea15c 100644
--- a/ruby.h
+++ b/ruby.h
@@ -596,6 +596,7 @@ ID rb_intern(const char*);
 ID rb_intern2(const char*, long);
 const char *rb_id2name(ID);
 ID rb_to_id(VALUE);
+VALUE rb_id2str(ID);
 
 char *rb_class2name(VALUE);
 char *rb_obj_classname(VALUE);