diff --git a/ndhc/clientpacket.c b/ndhc/clientpacket.c
index 5e9a64b..adcb25c 100644
--- a/ndhc/clientpacket.c
+++ b/ndhc/clientpacket.c
@@ -20,6 +20,7 @@
  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#include <stddef.h>
 #include <stdint.h>
 #include <string.h>
 #include <sys/socket.h>
diff --git a/ndhc/packet.c b/ndhc/packet.c
index ed6ff3a..09185a9 100644
--- a/ndhc/packet.c
+++ b/ndhc/packet.c
@@ -1,3 +1,4 @@
+#include <stddef.h>
 #include <unistd.h>
 #include <string.h>
 #include <netinet/in.h>