diff --git a/configure.ac b/configure.ac
index f44a5e2..b10ab8a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -9,6 +9,9 @@ AC_CONFIG_AUX_DIR([config/autoconf])
 AC_CANONICAL_BUILD
 AC_CANONICAL_HOST
 
+# If possible, enable extensions to Posix
+AC_USE_SYSTEM_EXTENSIONS
+
 #AM_MAINTAINER_MODE
 
 CFLAGS="${CFLAGS} -Wall"
@@ -91,7 +94,6 @@ AC_CHECK_DECL(N_SLCAN,,
 AC_CHECK_DECL(SCM_TIMESTAMPING_OPT_STATS,,
     [AC_DEFINE([SCM_TIMESTAMPING_OPT_STATS], [54], [SCM_TIMESTAMPING_OPT_STATS])]
 )
-AC_DEFINE(_GNU_SOURCE)
 
 
 #