--- src/knockd.c
+++ src/knockd.c
@@ -207,7 +207,7 @@
 
 	/* 50ms timeout for packet capture. See pcap(3pcap) manpage, which
 	 * recommends that a timeout of 0 not be used. */
-	cap = pcap_open_live(o_int, 65535, 0, 50, pcapErr);
+	cap = pcap_open_live(o_int, BUFSIZ, 0, 50, pcapErr);
 	if(strlen(pcapErr)) {
 		fprintf(stderr, "could not open %s: %s\n", o_int, pcapErr);
 	}