diff --git a/ndhc/clientpacket.c b/ndhc/clientpacket.c
index 96afc1e..8052f94 100644
--- a/ndhc/clientpacket.c
+++ b/ndhc/clientpacket.c
@@ -72,7 +72,7 @@ uint32_t random_xid(void)
 /* Initializes dhcp packet header for a -client- packet. */
 static void init_header(struct dhcpMessage *packet, char type)
 {
-    memset(packet, 0, sizeof(struct dhcpMessage));
+    memset(packet, 0, DHCP_SIZE);
     packet->op = BOOTREQUEST; /* client */
     packet->htype = ETH_10MB;
     packet->hlen = ETH_10MB_LEN;
diff --git a/ndhc/packet.c b/ndhc/packet.c
index 3f6fbbe..17de8db 100644
--- a/ndhc/packet.c
+++ b/ndhc/packet.c
@@ -19,8 +19,8 @@ int get_packet(struct dhcpMessage *packet, int fd)
 {
     int bytes;
 
-    memset(packet, 0, sizeof(struct dhcpMessage));
-    bytes = safe_read(fd, (char *)packet, sizeof(struct dhcpMessage));
+    memset(packet, 0, DHCP_SIZE);
+    bytes = safe_read(fd, (char *)packet, DHCP_SIZE);
     if (bytes == -1) {
 	log_line("Read on listen socket failed: %s", strerror(errno));
 	return -1;