diff --git a/src/remmina_unlock.c b/src/remmina_unlock.c
index 1a3de304ad8f0bae0fa7183e22537bf8c9e57bdc..d05000f7d81df824a12466d90baac9be0cf797ee 100644
--- a/src/remmina_unlock.c
+++ b/src/remmina_unlock.c
@@ -75,6 +75,7 @@ void remmina_unlock_timer_destroy()
 	TRACE_CALL(__func__);
 
 	g_timer_destroy(timer);
+	timer = NULL;
 }
 
 static void remmina_unlock_unlock_clicked(GtkButton *btn, gpointer user_data)