diff --git a/src/proto/window.pro b/src/proto/window.pro
index 93264e1..740d310 100644
--- a/src/proto/window.pro
+++ b/src/proto/window.pro
@@ -55,6 +55,7 @@
 void win_size_save(garray_T *gap);
 void win_size_restore(garray_T *gap);
 int win_comp_pos(void);
+void win_ensure_size(void);
 void win_setheight(int height);
 void win_setheight_win(int height, win_T *win);
 void win_setwidth(int width);