diff --git a/librb/configure.ac b/librb/configure.ac
index 52f0a230..26b85a9b 100644
--- a/librb/configure.ac
+++ b/librb/configure.ac
@@ -496,6 +496,7 @@ if test "x$rb_windows_h" = "xyes"; then
 	echo '#define WIN32_LEAN_AND_MEAN 1' >> $outfile
 	echo '#include <windows.h>' >> $outfile
 	echo '#include <winsock2.h>' >> $outfile
+	echo '#include <ws2tcpip.h>' >> $outfile
 	echo '#include <iphlpapi.h>' >> $outfile
 fi