diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 76ffce0c18ae..913c7fb51b18 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -710,8 +710,9 @@ static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb
 			min_t(unsigned int, eff_sacks,
 			      (remaining - TCPOLEN_SACK_BASE_ALIGNED) /
 			      TCPOLEN_SACK_PERBLOCK);
-		size += TCPOLEN_SACK_BASE_ALIGNED +
-			opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK;
+		if (likely(opts->num_sack_blocks))
+			size += TCPOLEN_SACK_BASE_ALIGNED +
+				opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK;
 	}
 
 	return size;