diff --git a/include/common/htx.h b/include/common/htx.h
index 55d4931..ec99098 100644
--- a/include/common/htx.h
+++ b/include/common/htx.h
@@ -139,6 +139,9 @@
 
 	/* XXX 2 bytes unused */
 
+	int32_t hdrs_bytes;  /* Bytes held by all headers from this start-line
+			      * to the corresponding EOH. -1 if unknown */
+
 	unsigned int len[3]; /* length of differnt parts of the start-line */
 	char         l[0];
 };
diff --git a/src/htx.c b/src/htx.c
index 3a2252f..bc2ecbd 100644
--- a/src/htx.c
+++ b/src/htx.c
@@ -633,6 +633,8 @@
 	sl = htx_get_blk_ptr(htx, blk);
 	sl->info = tmp.info;
 	sl->flags = tmp.flags;
+	if (sl->hdrs_bytes != -1)
+		sl->hdrs_bytes += delta;
 
 	HTX_SL_P1_LEN(sl) = p1.len;
 	HTX_SL_P2_LEN(sl) = p2.len;
@@ -669,7 +671,7 @@
 	sl = htx_get_blk_ptr(htx, blk);
 	if (htx->sl_pos == -1)
 		htx->sl_pos = htx_get_blk_pos(htx, blk);
-
+	sl->hdrs_bytes = -1;
 	sl->flags = flags;
 
 	HTX_SL_P1_LEN(sl) = p1.len;