diff --git a/tools/build/feature/test-gettid.c b/tools/build/feature/test-gettid.c
index ef24e42d3f1b..a8fdb2619669 100644
--- a/tools/build/feature/test-gettid.c
+++ b/tools/build/feature/test-gettid.c
@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0
 // Copyright (C) 2019, Red Hat Inc, Arnaldo Carvalho de Melo <acme@redhat.com>
+#undef _GNU_SOURCE
 #define _GNU_SOURCE
 #include <unistd.h>