diff --git a/src/event/ngx_event_pipe.h b/src/event/ngx_event_pipe.h
index 9781820..887f8b7 100644
--- a/src/event/ngx_event_pipe.h
+++ b/src/event/ngx_event_pipe.h
@@ -88,6 +88,7 @@
 
 ngx_int_t ngx_event_pipe(ngx_event_pipe_t *p, int do_write);
 ngx_int_t ngx_event_pipe_copy_input_filter(ngx_event_pipe_t *p, ngx_buf_t *buf);
+ngx_int_t ngx_event_pipe_add_free_buf(ngx_event_pipe_t *p, ngx_buf_t *b);
 
 
 #endif /* _NGX_EVENT_PIPE_H_INCLUDED_ */