diff --git a/src/os_unix.c b/src/os_unix.c
index 746bcff..5801965 100644
--- a/src/os_unix.c
+++ b/src/os_unix.c
@@ -2434,6 +2434,7 @@
 	    || STRCMP(name, "builtin_iris-ansi") == 0);
 }
 
+#if defined(VMS) || defined(PROTO)
 /*
  * Return TRUE if "name" is a vt300-like terminal name.
  */
@@ -2448,6 +2449,7 @@
 			     && vim_strchr((char_u *)"12345", name[2]) != NULL)
 	    || STRCMP(name, "builtin_vt320") == 0);
 }
+#endif
 
 /*
  * Insert user name in s[len].