diff --git a/src/proto/popupwin.pro b/src/proto/popupwin.pro
index dab117e..d6ba3e7 100644
--- a/src/proto/popupwin.pro
+++ b/src/proto/popupwin.pro
@@ -55,6 +55,7 @@
 int popup_create_preview_window(int info);
 void popup_close_preview(void);
 void popup_hide_info(void);
+int popup_win_closed(win_T *win);
 void popup_set_title(win_T *wp);
 void popup_update_preview_title(void);
 /* vim: set ft=c : */