diff --git a/arp.c b/arp.c
index 0aae069..2b4c664 100644
--- a/arp.c
+++ b/arp.c
@@ -55,7 +55,7 @@ void sendarp(int ifr_idx, const unsigned char* mac, in_addr_t ip)
 
 	memset(&sll, 0, sizeof(sll));
 	sll.sll_family = AF_PACKET;
-	memcpy(sll.sll_addr, mac, sizeof(sll.sll_addr) - 1);
+	memcpy(sll.sll_addr, mac, ETH_ALEN);
 	sll.sll_halen = ETH_ALEN;
 	sll.sll_ifindex = ifr_idx;