diff --git a/src/proto/option.pro b/src/proto/option.pro
index 12be870..c6dfc1b 100644
--- a/src/proto/option.pro
+++ b/src/proto/option.pro
@@ -88,6 +88,7 @@
 char *did_set_winminwidth(optset_T *args);
 char *did_set_winwidth(optset_T *args);
 char *did_set_wrap(optset_T *args);
+char *did_set_xhistory(optset_T *args);
 void check_redraw(long_u flags);
 int findoption(char_u *arg);
 getoption_T get_option_value(char_u *name, long *numval, char_u **stringval, int *flagsp, int scope);