diff --git a/configure.in b/configure.in
index 3d4c6404..10a72d35 100644
--- a/configure.in
+++ b/configure.in
@@ -105,7 +105,8 @@ AC_CHECK_HEADERS([ \
 	strings.h sys/socket.h sys/time.h unistd.h \
 	],,AC_MSG_ERROR([required C header missing!]))
 
-AC_CHECK_HEADERS([arpa/inet.h ctype.h malloc.h stdbool.h stddef.h varargs.h])
+AC_CHECK_HEADERS([ \
+	arpa/inet.h ctype.h malloc.h netinet/ip.h stdbool.h stddef.h varargs.h])
 
 # -- Datatypes --
 
diff --git a/contrib/MacOSX/config.h b/contrib/MacOSX/config.h
index 60b06188..66465e26 100644
--- a/contrib/MacOSX/config.h
+++ b/contrib/MacOSX/config.h
@@ -71,6 +71,8 @@
 #define HAVE_STDBOOL_H 1
 /* Define to 1 if you have the <arpa/inet.h> header file. */
 #define HAVE_ARPA_INET_H 1
+/* Define to 1 if you have the <netinet/ip.h> header file. */
+#define HAVE_NETINET_IP_H 1
 
 /* Define to 1 if you have the `kqueue' function. */
 #define HAVE_KQUEUE 1