diff --git a/include/proto/htx.h b/include/proto/htx.h
index 2f7aaf7..7db2059 100644
--- a/include/proto/htx.h
+++ b/include/proto/htx.h
@@ -57,6 +57,7 @@
 struct htx_blk *htx_add_data(struct htx *htx, const struct ist data);
 struct htx_blk *htx_add_trailer(struct htx *htx, const struct ist tlr);
 struct htx_blk *htx_add_oob(struct htx *htx, const struct ist oob);
+struct htx_blk *htx_add_data_before(struct htx *htx, const struct htx_blk *ref, const struct ist data);
 
 int htx_reqline_to_str(const union htx_sl *sl, struct buffer *chk);
 int htx_stline_to_str(const union htx_sl *sl, struct buffer *chk);