2 files changed, 3 insertions, 1 deletions

diff --git a/config.h.in b/config.h.in
index 1dedbb4..210b22a 100644
--- a/config.h.in
+++ b/config.h.in
@@ -71,3 +71,6 @@
 
 /* Version number of package */
 #undef VERSION
+
+/* _GNU_SOURCE required for readahead (linux) */
+#undef _GNU_SOURCE
diff --git a/libeio.m4 b/libeio.m4
index ba866d8..d2b8030 100644
--- a/libeio.m4
+++ b/libeio.m4
@@ -21,7 +21,6 @@ int main(void)
 test $ac_cv_futimes = yes && AC_DEFINE(HAVE_FUTIMES, 1, futimes(2) is available)
 
 AC_CACHE_CHECK(for readahead, ac_cv_readahead, [AC_LINK_IFELSE([
-#define _GNU_SOURCE
 #include <fcntl.h>
 int main(void)
 {