--- a/ping.c
+++ b/ping.c
@@ -813,7 +813,7 @@
 	int    rv;
 
 	buf = malloc(len*sizeof(char));
-	memset(buf, 0, sizeof(buf));
+	memset(buf, 0, len*sizeof(char));
 
 	while (1) {
 		rv = gethostbyname_r(hostname, &result_buf, buf, len,