diff --git a/src/h3.c b/src/h3.c
index b6df43045..e3ee84694 100644
--- a/src/h3.c
+++ b/src/h3.c
@@ -126,9 +126,12 @@ static int h3_decode_qcs(struct qcs *qcs, int fin, void *ctx)
 
 		h3_debug_printf(stderr, "%s: ftype: %llu, flen: %llu\n", __func__,
 		        (unsigned long long)ftype, (unsigned long long)flen);
-		if (flen > b_data(&b))
+		if (flen > b_data(&b) && !b_full(rxbuf))
 			break;
 
+		/* TODO handle full rxbuf */
+		BUG_ON(flen > b_size(rxbuf));
+
 		b_del(rxbuf, hlen);
 		last_stream_frame = (fin && flen == b_data(rxbuf));