diff --git a/clients/window.h b/clients/window.h
index 871e46b8..de7ccce0 100644
--- a/clients/window.h
+++ b/clients/window.h
@@ -157,6 +157,9 @@ window_copy_surface(struct window *window,
 void
 window_flush(struct window *window);
 
+void
+window_set_surface(struct window *window, cairo_surface_t *surface);
+
 void
 window_create_surface(struct window *window);