diff --git a/src/proto/typval.pro b/src/proto/typval.pro
index 9c57226..eafc0e6 100644
--- a/src/proto/typval.pro
+++ b/src/proto/typval.pro
@@ -9,6 +9,7 @@
 varnumber_T tv_get_bool(typval_T *varp);
 varnumber_T tv_get_bool_chk(typval_T *varp, int *denote);
 float_T tv_get_float(typval_T *varp);
+int check_for_string(typval_T *tv);
 char_u *tv_get_string(typval_T *varp);
 char_u *tv_get_string_buf(typval_T *varp, char_u *buf);
 char_u *tv_get_string_chk(typval_T *varp);