diff --git a/src/proto/option.pro b/src/proto/option.pro
index 39ee7be..9c58c3e 100644
--- a/src/proto/option.pro
+++ b/src/proto/option.pro
@@ -29,6 +29,7 @@
 int makefoldset __ARGS((FILE *fd));
 void clear_termoptions __ARGS((void));
 void free_termoptions __ARGS((void));
+void free_one_termoption __ARGS((char_u *var));
 void set_term_defaults __ARGS((void));
 void comp_col __ARGS((void));
 char_u *get_equalprg __ARGS((void));