diff --git a/include/common/htx.h b/include/common/htx.h
index b22da99..11caa59 100644
--- a/include/common/htx.h
+++ b/include/common/htx.h
@@ -255,6 +255,7 @@
 size_t htx_add_data(struct htx *htx, const struct ist data);
 struct htx_blk *htx_add_last_data(struct htx *htx, struct ist data);
 void htx_move_blk_before(struct htx *htx, struct htx_blk **blk, struct htx_blk **ref);
+int htx_append_msg(struct htx *dst, const struct htx *src);
 
 /* Functions and macros to get parts of the start-line or legnth of these
  * parts. Request and response start-lines are both composed of 3 parts.