diff --git a/arpwatch.c b/arpwatch.c
index c570ce8..d2500f7 100644
--- a/arpwatch.c
+++ b/arpwatch.c
@@ -730,11 +730,12 @@ addnet(register const char *str)
 
 	/* XXX hack */
 	n = ntohl(inet_addr(tstr));
-	while ((n & 0xff000000) == 0) {
-		n <<= 8;
-		if (n == 0)
-			return (0);
-	}
+	if (n || width != 32)
+		while ((n & 0xff000000) == 0) {
+			n <<= 8;
+			if (n == 0)
+				return (0);
+		}
 	n = htonl(n);
 
 	if (width != 0) {