diff --git a/src/proto/popupwin.pro b/src/proto/popupwin.pro
index e026506..1eb2c10 100644
--- a/src/proto/popupwin.pro
+++ b/src/proto/popupwin.pro
@@ -21,7 +21,7 @@
 void f_popup_move(typval_T *argvars, typval_T *rettv);
 void f_popup_getpos(typval_T *argvars, typval_T *rettv);
 void f_popup_getoptions(typval_T *argvars, typval_T *rettv);
-int not_in_popup_window(void);
+int error_if_popup_window(void);
 void popup_reset_handled(void);
 win_T *find_next_popup(int lowest);
 int popup_do_filter(int c);