diff --git a/include/arpa/inet.h b/include/arpa/inet.h
index 9c9554e5a625..42daebf13c5d 100644
--- a/include/arpa/inet.h
+++ b/include/arpa/inet.h
@@ -64,6 +64,14 @@
 /* Required for byteorder(3) functions. */
 #include <machine/endian.h>
 
+#ifndef INET_ADDRSTRLEN
+#define	INET_ADDRSTRLEN		16
+#endif
+
+#ifndef INET6_ADDRSTRLEN
+#define	INET6_ADDRSTRLEN	46
+#endif
+
 #ifndef	_IN_ADDR_T_DECLARED_
 typedef	__uint32_t	in_addr_t;
 #define	_IN_ADDR_T_DECLARED_
@@ -82,8 +90,8 @@ typedef	_BSD_SIZE_T_	size_t;
 #endif /* !_POSIX_SOURCE */
 
 /*
- * XXX socklen_t is used by a POSIX.1-200x interface, but not required by
- * POSIX.1-200x.
+ * XXX socklen_t is used by a POSIX.1-2001 interface, but not required by
+ * POSIX.1-2001.
  */
 #ifdef	_BSD_SOCKLEN_T_
 typedef	_BSD_SOCKLEN_T_	socklen_t;
@@ -97,6 +105,10 @@ struct in_addr {
 #define	_STRUCT_IN_ADDR_DECLARED
 #endif
 
+/*
+ * XXX missing typedefs for uint16_t and uint32_t.
+ */
+
 /* XXX all new diversions!! argh!! */
 #ifndef _POSIX_SOURCE
 #define	inet_addr	__inet_addr
diff --git a/sys/netinet/in.h b/sys/netinet/in.h
index 819a82773eb8..973d0af08aa6 100644
--- a/sys/netinet/in.h
+++ b/sys/netinet/in.h
@@ -306,7 +306,9 @@ struct sockaddr_in {
 	char	sin_zero[8];
 };
 
+#ifndef INET_ADDRSTRLEN
 #define	INET_ADDRSTRLEN                 16
+#endif
 
 /*
  * Options for use with [gs]etsockopt at the IP level.
diff --git a/sys/netinet6/in6.h b/sys/netinet6/in6.h
index b16af5f6cc73..39cda5db8e90 100644
--- a/sys/netinet6/in6.h
+++ b/sys/netinet6/in6.h
@@ -132,7 +132,9 @@ struct in6_addr {
 #define s6_addr32 __u6_addr.__u6_addr32
 #endif
 
+#ifndef INET6_ADDRSTRLEN
 #define INET6_ADDRSTRLEN	46
+#endif
 
 /*
  * Socket address for IPv6