diff --git a/configure.ac b/configure.ac
index 42f0dc4c..baec6697 100644
--- a/configure.ac
+++ b/configure.ac
@@ -23,6 +23,9 @@ AM_CONDITIONAL([BUILD_MAN], [test "x$enable_man_doc" = "xyes" ])
 
 # Checks for programs.
 AC_PROG_CC
+
+AC_USE_SYSTEM_EXTENSIONS
+
 AC_PROG_MKDIR_P
 AC_PROG_INSTALL
 AC_PROG_SED
diff --git a/include/nft.h b/include/nft.h
index 4e66f8e6..0fd481c6 100644
--- a/include/nft.h
+++ b/include/nft.h
@@ -2,8 +2,6 @@
 #ifndef NFTABLES_NFT_H
 #define NFTABLES_NFT_H
 
-#define _GNU_SOURCE
-
 #include <config.h>
 
 #endif /* NFTABLES_NFT_H */