diff --git a/ninfod/ninfod.h b/ninfod/ninfod.h
index d4e7d679..94c895ec 100644
--- a/ninfod/ninfod.h
+++ b/ninfod/ninfod.h
@@ -31,6 +31,8 @@
  * Author:
  * 	YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
  */
+#ifndef IPUTILS_NINFOD_H
+#define IPUTILS_NINFOD_H
 
 /* definitions */
 #define NINFOD			"ninfod"
@@ -118,3 +120,4 @@ int pr_nodeinfo_ipv4addr(CHECKANDFILL_ARGS);
 void init_nodeinfo_nodename(INIT_ARGS);
 int pr_nodeinfo_nodename(CHECKANDFILL_ARGS);
 
+#endif /* IPUTILS_NINFOD_H */
diff --git a/ping/ping.h b/ping/ping.h
index 20ac3e8c..a90c4665 100644
--- a/ping/ping.h
+++ b/ping/ping.h
@@ -1,3 +1,6 @@
+#ifndef IPUTILS_PING_H
+#define IPUTILS_PING_H
+
 /* Includes */
 #include <stdio.h>
 #include <stdlib.h>
@@ -409,3 +412,5 @@ struct ni_hdr {
 #define ni_cksum	ni_u.icmp6_cksum
 #define ni_qtype	ni_u.icmp6_data16[0]
 #define ni_flags	ni_u.icmp6_data16[1]
+
+#endif /* IPUTILS_PING_H */
diff --git a/tftpd/tftp.h b/tftpd/tftp.h
index c8393cc8..e7dfba13 100644
--- a/tftpd/tftp.h
+++ b/tftpd/tftp.h
@@ -1,3 +1,5 @@
+#ifndef IPUTILS_TFTPD_H
+#define IPUTILS_TFTPD_H
 /*
  * Copyright (c) 1983, 1993
  *	The Regents of the University of California.  All rights reserved.
@@ -38,3 +40,5 @@ extern int write_behind(FILE *file, int convert);
 extern int synchnet(int f);
 extern struct tftphdr *w_init(void);
 extern struct tftphdr *r_init(void);
+
+#endif /* IPUTILS_TFTPD_H */