diff --git a/tap.c b/tap.c
index f638f2c..a3ba958 100644
--- a/tap.c
+++ b/tap.c
@@ -1084,7 +1084,7 @@ static void tap_pasta_input(struct ctx *c, const struct timespec *now)
 
 	tap_flush_pools();
 
-	for (n = 0; n <= (ssize_t)TAP_BUF_BYTES - ETH_MAX_MTU; n += len) {
+	for (n = 0; n <= (ssize_t)(TAP_BUF_BYTES - ETH_MAX_MTU); n += len) {
 		len = read(c->fd_tap, pkt_buf + n, ETH_MAX_MTU);
 
 		if (len == 0) {