diff --git a/src/proto/eval.pro b/src/proto/eval.pro
index 07b11b2..03630c4 100644
--- a/src/proto/eval.pro
+++ b/src/proto/eval.pro
@@ -25,7 +25,7 @@
 int eval_foldexpr(char_u *arg, int *cp);
 char_u *get_lval(char_u *name, typval_T *rettv, lval_T *lp, int unlet, int skip, int flags, int fne_flags);
 void clear_lval(lval_T *lp);
-void set_var_lval(lval_T *lp, char_u *endp, typval_T *rettv, int copy, int flags, char_u *op);
+void set_var_lval(lval_T *lp, char_u *endp, typval_T *rettv, int copy, int flags, char_u *op, int var_idx);
 void *eval_for_line(char_u *arg, int *errp, exarg_T *eap, evalarg_T *evalarg);
 void skip_for_lines(void *fi_void, evalarg_T *evalarg);
 int next_for_item(void *fi_void, char_u *arg);