diff --git a/gnu/usr.bin/cc/libiberty/config.h b/gnu/usr.bin/cc/libiberty/config.h
index 0fc8ed6ebb57..236e07689498 100644
--- a/gnu/usr.bin/cc/libiberty/config.h
+++ b/gnu/usr.bin/cc/libiberty/config.h
@@ -235,7 +235,7 @@
 #define HAVE_STRNCASECMP 1
 
 /* Define to 1 if you have the `strndup' function. */
-/* #undef HAVE_STRNDUP */
+#define HAVE_STRNDUP 1
 
 /* Define to 1 if you have the `strrchr' function. */
 #define HAVE_STRRCHR 1
diff --git a/gnu/usr.bin/sort/config.h b/gnu/usr.bin/sort/config.h
index 44f944c04b0c..601b368d42fc 100644
--- a/gnu/usr.bin/sort/config.h
+++ b/gnu/usr.bin/sort/config.h
@@ -759,7 +759,7 @@
 #define HAVE_STRNCASECMP 1
 
 /* Define to 1 if you have the `strndup' function. */
-/* #undef HAVE_STRNDUP */
+#define HAVE_STRNDUP 1
 
 /* Define to 1 if you have the `strpbrk' function. */
 #define HAVE_STRPBRK 1
diff --git a/include/string.h b/include/string.h
index 1b6e1849de43..32a9ad3e5608 100644
--- a/include/string.h
+++ b/include/string.h
@@ -96,6 +96,7 @@ char	*strncat(char * __restrict, const char * __restrict, size_t);
 int	 strncmp(const char *, const char *, size_t) __pure;
 char	*strncpy(char * __restrict, const char * __restrict, size_t);
 #if __BSD_VISIBLE
+char	*strndup(const char *, size_t);
 char	*strnstr(const char *, const char *, size_t) __pure;
 #endif
 char	*strpbrk(const char *, const char *) __pure;
diff --git a/kerberos5/include/config.h b/kerberos5/include/config.h
index 4484060d3c1a..f4b6d1e580c9 100644
--- a/kerberos5/include/config.h
+++ b/kerberos5/include/config.h
@@ -785,7 +785,7 @@ static /**/const char *const rcsid[] = { (const char *)rcsid, "@(#)" msg }
 #define HAVE_STRNCASECMP 1
 
 /* Define if you have the function `strndup'. */
-/* #undef HAVE_STRNDUP */
+#define HAVE_STRNDUP 1
 
 /* Define if you have the function `strnlen'. */
 /* #undef HAVE_STRNLEN */
diff --git a/lib/bind/bind/port_after.h b/lib/bind/bind/port_after.h
index 38335d6fc618..f0b7f82d7b52 100644
--- a/lib/bind/bind/port_after.h
+++ b/lib/bind/bind/port_after.h
@@ -30,7 +30,7 @@
 #undef HAS_IN_ADDR6
 #define HAVE_SOCKADDR_STORAGE 1
 #undef NEED_GETTIMEOFDAY
-#undef HAVE_STRNDUP
+#define HAVE_STRNDUP 1
 #undef USE_FIONBIO_IOCTL
 #undef USE_SYSERROR_LIST
 #undef INNETGR_ARGS
diff --git a/lib/libmagic/config.h b/lib/libmagic/config.h
index 65e4a6a59ad9..4f8a99f6cca2 100644
--- a/lib/libmagic/config.h
+++ b/lib/libmagic/config.h
@@ -77,7 +77,7 @@
 #define HAVE_STRING_H 1
 
 /* Define to 1 if you have the `strndup' function. */
-/* #undef HAVE_STRNDUP */
+#define HAVE_STRNDUP 1
 
 /* Define to 1 if you have the `strtof' function. */
 #define HAVE_STRTOF 1
diff --git a/usr.bin/file/config.h b/usr.bin/file/config.h
index 65e4a6a59ad9..4f8a99f6cca2 100644
--- a/usr.bin/file/config.h
+++ b/usr.bin/file/config.h
@@ -77,7 +77,7 @@
 #define HAVE_STRING_H 1
 
 /* Define to 1 if you have the `strndup' function. */
-/* #undef HAVE_STRNDUP */
+#define HAVE_STRNDUP 1
 
 /* Define to 1 if you have the `strtof' function. */
 #define HAVE_STRTOF 1