Index: configure.ac
==================================================================
--- configure.ac
+++ configure.ac
@@ -48,11 +48,11 @@
 
 AC_CHECK_LIB(dl, dlopen, LIBS="$LIBS -ldl")
 
 AC_CHECK_FUNC(asprintf, [
 	have_asprintf="yes"
-	AC_DEFINE(HAVE_ASPRINTF, 1, "Whether we have asprintf")], [
+	AC_DEFINE(HAVE_ASPRINTF, 1, [Whether we have asprintf])], [
 	have_asprintf="no"
 	AC_SUBST(ASPRINTF_C, "asprintf.c")])
 
 AC_MSG_CHECKING(whether snprintf returns something useful)
 AC_CACHE_VAL(ac_cv_snprintf_useful_ret, [
@@ -119,11 +119,11 @@
 		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)
+AC_CHECK_FUNC(madvise, [AC_DEFINE(HAVE_MADVISE, 1, [Whether we have madvise])])
 
 AC_LANG([Objective C])
 AC_PROG_OBJC
 
 OBJCFLAGS="$OBJCFLAGS -Wall -fobjc-exceptions"

Index: src/OFMutableString.m
==================================================================
--- src/OFMutableString.m
+++ src/OFMutableString.m
@@ -16,11 +16,11 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <ctype.h>
 
-#ifdef HAVE_SYS_MMAN_H
+#ifdef HAVE_MADVISE
 #include <sys/mman.h>
 #else
 #define madvise(addr, len, advise)
 #endif
 

Index: src/OFString.m
==================================================================
--- src/OFString.m
+++ src/OFString.m
@@ -14,11 +14,11 @@
 #define _GNU_SOURCE
 #include <stdarg.h>
 #include <stdlib.h>
 #include <string.h>
 
-#ifdef HAVE_SYS_MMAN_H
+#ifdef HAVE_MADVISE
 #include <sys/mman.h>
 #else
 #define madvise(addr, len, advise)
 #endif