diff --git a/ChangeLog b/ChangeLog
index ed04766f2b..5cf025870a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Mon Sep 23 05:07:49 2013  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* include/ruby/intern.h (rb_ary_cat): move from internal.h, since it
+	  is described in README.EXT.
+
 Sun Sep 22 20:55:20 2013  Kazuki Tsujimoto  <kazuki@callcc.net>
 
 	* vm_insnhelper.c (vm_make_proc_with_iseq): fix bug message.
diff --git a/include/ruby/intern.h b/include/ruby/intern.h
index 0ba0e6e6b2..757699bd91 100644
--- a/include/ruby/intern.h
+++ b/include/ruby/intern.h
@@ -63,6 +63,7 @@ VALUE rb_ary_dup(VALUE);
 VALUE rb_ary_resurrect(VALUE ary);
 VALUE rb_ary_to_ary(VALUE);
 VALUE rb_ary_to_s(VALUE);
+VALUE rb_ary_cat(VALUE, const VALUE *, long);
 VALUE rb_ary_push(VALUE, VALUE);
 VALUE rb_ary_pop(VALUE);
 VALUE rb_ary_shift(VALUE);
diff --git a/internal.h b/internal.h
index 795749dd5b..7036398bc7 100644
--- a/internal.h
+++ b/internal.h
@@ -316,7 +316,6 @@ struct vtm; /* defined by timev.h */
 /* array.c */
 VALUE rb_ary_last(int, VALUE *, VALUE);
 void rb_ary_set_len(VALUE, long);
-VALUE rb_ary_cat(VALUE, const VALUE *, long);
 void rb_ary_delete_same(VALUE, VALUE);
 
 /* bignum.c */