diff --git a/src/proto/vim9execute.pro b/src/proto/vim9execute.pro
index 5712fcf..8b4b6ea 100644
--- a/src/proto/vim9execute.pro
+++ b/src/proto/vim9execute.pro
@@ -4,6 +4,7 @@
 char_u *char_from_string(char_u *str, varnumber_T index);
 char_u *string_slice(char_u *str, varnumber_T first, varnumber_T last, int exclusive);
 int fill_partial_and_closure(partial_T *pt, ufunc_T *ufunc, ectx_T *ectx);
+typval_T *lookup_debug_var(char_u *name);
 int exe_typval_instr(typval_T *tv, typval_T *rettv);
 char_u *exe_substitute_instr(void);
 int call_def_function(ufunc_T *ufunc, int argc_arg, typval_T *argv, partial_T *partial, typval_T *rettv);