diff --git a/m4/sys_socket_h.m4 b/m4/sys_socket_h.m4
deleted file mode 100644
index d3e45b4..0000000
--- a/m4/sys_socket_h.m4
+++ /dev/null
@@ -1,23 +0,0 @@
-# sys_socket_h.m4 serial 2
-dnl Copyright (C) 2005, 2006 Free Software Foundation, Inc.
-dnl This file is free software; the Free Software Foundation
-dnl gives unlimited permission to copy and/or distribute it,
-dnl with or without modifications, as long as this notice is preserved.
-
-dnl From Simon Josefsson.
-
-AC_DEFUN([gl_HEADER_SYS_SOCKET],
-[
-  AC_CHECK_HEADERS_ONCE([sys/socket.h])
-  if test $ac_cv_header_sys_socket_h = yes; then
-    SYS_SOCKET_H=''
-  else
-    dnl We cannot use AC_CHECK_HEADERS_ONCE here, because that would make
-    dnl the check for those headers unconditional; yet cygwin reports
-    dnl that the headers are present but cannot be compiled (since on
-    dnl cygwin, all socket information should come from sys/socket.h).
-    AC_CHECK_HEADERS([winsock2.h ws2tcpip.h])
-    SYS_SOCKET_H='sys/socket.h'
-  fi
-  AC_SUBST(SYS_SOCKET_H)
-])