diff --git a/src/proto/typval.pro b/src/proto/typval.pro
index f04bf15..b744bbc 100644
--- a/src/proto/typval.pro
+++ b/src/proto/typval.pro
@@ -57,6 +57,7 @@
 void copy_tv(typval_T *from, typval_T *to);
 int typval_compare(typval_T *tv1, typval_T *tv2, exprtype_T type, int ic);
 int typval_compare_list(typval_T *tv1, typval_T *tv2, exprtype_T type, int ic, int *res);
+int typval_compare_null(typval_T *tv1, typval_T *tv2);
 int typval_compare_blob(typval_T *tv1, typval_T *tv2, exprtype_T type, int *res);
 int typval_compare_dict(typval_T *tv1, typval_T *tv2, exprtype_T type, int ic, int *res);
 int typval_compare_func(typval_T *tv1, typval_T *tv2, exprtype_T type, int ic, int *res);