Index: configure.ac
==================================================================
--- configure.ac
+++ configure.ac
@@ -98,10 +98,12 @@
 		ac_cv_have_ipv6="no",
 		ac_cv_have_ipv6="no")])
 AC_MSG_RESULT($ac_cv_have_ipv6)
 test x"$ac_cv_have_ipv6" = x"yes" && \
 	AC_DEFINE(HAVE_IPV6, 1, "Whether we have IPv6 support")
+
+AC_CHECK_HEADERS(sys/mman.h)
 
 test x"$GCC" = x"yes" && CFLAGS="$CFLAGS -Werror -pipe -g"
 test x"$GCC" = x"yes" && OBJCFLAGS="$OBJCFLAGS -Werror -pipe -g"
 
 if test x"$cross_compiling" = x"yes"; then

Index: src/OFString.m
==================================================================
--- src/OFString.m
+++ src/OFString.m
@@ -13,11 +13,11 @@
 
 #import <stdlib.h>
 #import <string.h>
 #import <ctype.h>
 
-#ifndef _WIN32
+#ifdef HAVE_SYS_MMAN_H
 #import <sys/mman.h>
 #else
 #define madvise(addr, len, advise)
 #endif
 

Index: src/OFTCPSocket.h
==================================================================
--- src/OFTCPSocket.h
+++ src/OFTCPSocket.h
@@ -16,11 +16,10 @@
  */
 #ifndef _WIN32
 #import <sys/types.h>
 #import <sys/socket.h>
 #import <netdb.h>
-#else
 #endif
 
 #import "OFObject.h"
 #import "OFStream.h"