diff --git a/userspace/wrsw_rtud/rtu_fd.c b/userspace/wrsw_rtud/rtu_fd.c
index c7eccb9dc4a2e85dc7a74cb2189e1ec80711460b..1b7b79ef4f5109f0a1991b287e073446ee76ca4e 100644
--- a/userspace/wrsw_rtud/rtu_fd.c
+++ b/userspace/wrsw_rtud/rtu_fd.c
@@ -437,9 +437,8 @@ int rtu_fd_set_aging_time(unsigned long t)
  */
 void rtu_fd_flush(void)
 {
-	rtu_fd_age_update();	// Update filtering entries age
-
 	pthread_mutex_lock(&fd_mutex);
+	rtu_fd_age_update();	// Update filtering entries age
 	rtu_fd_age_out();	// Remove old entries
 	pthread_mutex_unlock(&fd_mutex);
 }