diff --git a/src/proto/json.pro b/src/proto/json.pro
index 926c2be..f05c131 100644
--- a/src/proto/json.pro
+++ b/src/proto/json.pro
@@ -1,6 +1,7 @@
 /* json.c */
 char_u *json_encode(typval_T *val, int options);
 char_u *json_encode_nr_expr(int nr, typval_T *val, int options);
+char_u *json_encode_lsp_msg(typval_T *val);
 int json_decode(js_read_T *reader, typval_T *res, int options);
 int json_find_end(js_read_T *reader, int options);
 void f_js_decode(typval_T *argvars, typval_T *rettv);