diff --git a/configure.ac b/configure.ac
index 50dae0a..57ccdaa 100644
--- a/configure.ac
+++ b/configure.ac
@@ -13,7 +13,7 @@ AC_PROG_LIBTOOL
 
 # Checks for header files.
 AC_HEADER_STDC
-AC_CHECK_HEADERS([arpa/inet.h fcntl.h netinet/in.h stdlib.h string.h sys/ioctl.h sys/socket.h sys/time.h termios.h unistd.h])
+AC_CHECK_HEADERS([termios.h sys/time.h unistd.h errno.h limits.h fcntl.h sys/types.h sys/socket.h sys/ioctl.h netinet/in.h netinet/ip.h netinet/tcp.h arpa/inet.h])
 
 # Checks for typedefs, structures, and compiler characteristics.
 AC_C_CONST