diff --git a/include/common/htx.h b/include/common/htx.h
index 9631c61..7d15365 100644
--- a/include/common/htx.h
+++ b/include/common/htx.h
@@ -470,7 +470,41 @@
 }
 
 /* Changes the size of the value. It is the caller responsibility to change the
- * value itself, make sure there is enough space and update allocated value.
+ * value itself, make sure there is enough space and update allocated
+ * value. This function updates the HTX message accordingly.
+ */
+static inline void htx_change_blk_value_len(struct htx *htx, struct htx_blk *blk, uint32_t newlen)
+{
+	enum htx_blk_type type = htx_get_blk_type(blk);
+	uint32_t oldlen, sz;
+	int32_t delta;
+
+	sz = htx_get_blksz(blk);
+	switch (type) {
+		case HTX_BLK_HDR:
+		case HTX_BLK_TLR:
+			oldlen = (blk->info >> 8) & 0xfffff;
+			blk->info = (type << 28) + (newlen << 8) + (blk->info & 0xff);
+			break;
+		default:
+			oldlen = blk->info & 0xfffffff;
+			blk->info = (type << 28) + newlen;
+			break;
+	}
+
+	/* Update HTTP message */
+	delta = (newlen - oldlen);
+	htx->data += delta;
+	if (blk->addr+sz == htx->tail_addr)
+		htx->tail_addr += delta;
+	else if (blk->addr+sz == htx->head_addr)
+		htx->head_addr += delta;
+}
+
+/* Changes the size of the value. It is the caller responsibility to change the
+ * value itself, make sure there is enough space and update allocated
+ * value. Unlike the function htx_change_blk_value_len(), this one does not
+ * update the HTX message. So it should be used with caution.
  */
 static inline void htx_set_blk_value_len(struct htx_blk *blk, uint32_t vlen)
 {