diff --git a/src/optionstr.c b/src/optionstr.c
index c03d994..ddb6c50 100644
--- a/src/optionstr.c
+++ b/src/optionstr.c
@@ -21,7 +21,7 @@
 				 "hangul", "insertmode", "lang", "mess",
 				 "showmatch", "operator", "register", "shell",
 				 "spell", "wildmode", NULL};
-static char *(p_nf_values[]) = {"bin", "octal", "hex", "alpha", NULL};
+static char *(p_nf_values[]) = {"bin", "octal", "hex", "alpha", "unsigned", NULL};
 static char *(p_ff_values[]) = {FF_UNIX, FF_DOS, FF_MAC, NULL};
 #ifdef FEAT_CRYPT
 static char *(p_cm_values[]) = {"zip", "blowfish", "blowfish2", NULL};