$NetBSD$

--- configure.ac
+++ configure.ac
@@ -40,7 +40,7 @@ AC_CHECK_LIB([nbcompat], [main], [LIBS="-lnbcompat $LIBS"])
 # Checks for header files.
 AC_CHECK_HEADERS([string.h strings.h memory.h stdlib.h unistd.h queue.h	\
 	sys/types.h sys/queue.h nbcompat/queue.h assert.h stddef.h	\
-	sys/socket.h netdb.h])
+	sys/socket.h netdb.h netinet/in.h netinet6/in6.h])
 CL_IFDEF(SLIST_HEAD, [SLIST_HEAD(name,type)],
 	[struct name { struct type *slh_first; /* first element */ }],
 	[Singly-linked list head])
