diff --git a/include/picrin.h b/include/picrin.h
index a1428268..3007db00 100644
--- a/include/picrin.h
+++ b/include/picrin.h
@@ -216,6 +216,10 @@ static inline void pic_warn(pic_state *pic, const char *msg)
 
 const char *pic_errmsg(pic_state *);
 
+struct pic_port *pic_stdin(pic_state *);
+struct pic_port *pic_stdout(pic_state *);
+struct pic_port *pic_stderr(pic_state *);
+
 pic_value pic_write(pic_state *, pic_value); /* returns given obj */
 pic_value pic_fwrite(pic_state *, pic_value, xFILE *);
 void pic_printf(pic_state *, const char *, ...);
diff --git a/include/picrin/port.h b/include/picrin/port.h
index 334746cb..4f763902 100644
--- a/include/picrin/port.h
+++ b/include/picrin/port.h
@@ -33,10 +33,6 @@ struct pic_port {
 
 pic_value pic_eof_object();
 
-struct pic_port *pic_stdin(pic_state *);
-struct pic_port *pic_stdout(pic_state *);
-struct pic_port *pic_stderr(pic_state *);
-
 struct pic_port *pic_open_input_string(pic_state *, const char *);
 struct pic_port *pic_open_output_string(pic_state *);
 struct pic_string *pic_get_output_string(pic_state *, struct pic_port *);