diff --git a/src/proto/optionstr.pro b/src/proto/optionstr.pro
index e021ad3..3163ba7 100644
--- a/src/proto/optionstr.pro
+++ b/src/proto/optionstr.pro
@@ -20,6 +20,7 @@
 char *did_set_bufhidden(optset_T *args);
 char *did_set_buftype(optset_T *args);
 char *did_set_casemap(optset_T *args);
+char *did_set_chars_option(optset_T *args);
 char *did_set_cinoptions(optset_T *args);
 char *did_set_colorcolumn(optset_T *args);
 char *did_set_comments(optset_T *args);