diff --git a/include/common/htx.h b/include/common/htx.h
index 79a9a13..0eabf24 100644
--- a/include/common/htx.h
+++ b/include/common/htx.h
@@ -171,6 +171,7 @@
 struct htx_blk *htx_add_blk(struct htx *htx, enum htx_blk_type type, uint32_t blksz);
 struct htx_blk *htx_remove_blk(struct htx *htx, struct htx_blk *blk);
 void htx_truncate(struct htx *htx, uint32_t offset);
+struct htx_ret htx_drain(struct htx *htx, uint32_t max);
 
 struct htx_blk *htx_replace_blk_value(struct htx *htx, struct htx_blk *blk,
 				      const struct ist old, const struct ist new);