diff --git a/sys/v4l2/gstv4l2allocator.c b/sys/v4l2/gstv4l2allocator.c
index 2bc51c48a2..a5c96269c4 100644
--- a/sys/v4l2/gstv4l2allocator.c
+++ b/sys/v4l2/gstv4l2allocator.c
@@ -21,6 +21,10 @@
 
 #include "config.h"
 
+#ifndef _GNU_SOURCE
+# define _GNU_SOURCE            /* O_CLOEXEC */
+#endif
+
 #include "ext/videodev2.h"
 #include "gstv4l2allocator.h"
 #include "v4l2_calls.h"