diff --git a/README.EXT b/README.EXT
index c8c9342..a660d43 100644
--- a/README.EXT
+++ b/README.EXT
@@ -311,6 +311,10 @@ To define nested classes or modules, use the functions below:
   VALUE rb_define_class_under(VALUE outer, const char *name, VALUE super)
   VALUE rb_define_module_under(VALUE outer, const char *name)
 
+To look up a constant by a C string, use the function below:
+
+  VALUE rb_path2class(const char *path)
+
 2.1.2 Method/singleton method definition
 
 To define methods or singleton methods, use these functions:
diff --git a/README.EXT.ja b/README.EXT.ja
index ce2b304..92d41da 100644
--- a/README.EXT.ja
+++ b/README.EXT.ja
@@ -348,6 +348,10 @@ Rubyで提供されている関数を使えばRubyインタプリタに新しい
   VALUE rb_define_class_under(VALUE outer, const char *name, VALUE super)
   VALUE rb_define_module_under(VALUE outer, const char *name)
 
+C の文字列で Ruby クラスを見つけたい時に、以下の関数を使って下さい。
+
+  VALUE rb_path2class(const char *path)
+
 2.1.2 メソッド/特異メソッド定義
 
 メソッドや特異メソッドを定義するには以下の関数を使います．
diff --git a/include/ruby/intern.h b/include/ruby/intern.h
index 6756941..9978410 100644
--- a/include/ruby/intern.h
+++ b/include/ruby/intern.h
@@ -862,7 +862,6 @@ VALUE rb_class_path(VALUE);
 void rb_set_class_path(VALUE, VALUE, const char*);
 void rb_set_class_path_string(VALUE, VALUE, VALUE);
 VALUE rb_path_to_class(VALUE);
-VALUE rb_path2class(const char*);
 void rb_name_class(VALUE, ID);
 VALUE rb_class_name(VALUE);
 void rb_autoload(VALUE, ID, const char*);
diff --git a/include/ruby/ruby.h b/include/ruby/ruby.h
index 7e534eb..c2c2505 100644
--- a/include/ruby/ruby.h
+++ b/include/ruby/ruby.h
@@ -1074,6 +1074,7 @@ VALUE rb_define_class(const char*,VALUE);
 VALUE rb_define_module(const char*);
 VALUE rb_define_class_under(VALUE, const char*, VALUE);
 VALUE rb_define_module_under(VALUE, const char*);
+VALUE rb_path2class(const char*);
 
 void rb_include_module(VALUE,VALUE);
 void rb_extend_object(VALUE,VALUE);