1 files changed, 3 insertions, 1 deletions
diff --git a/lib.c b/lib.c
index 4fdcaacf..c3428c22 100644
--- a/lib.c
+++ b/lib.c
@@ -4631,7 +4631,9 @@ val sub_str(val str_in, val from, val to)
 
   if (ge(from, to)) {
     return null_string;
-  } else if (from == zero && eql(to, len)) {
+  } else if (from == zero && eql(to, len) &&
+             (opt_compat == 0 || opt_compat > 215))
+  {
     return str_in;
   } else {
     size_t nchar = c_num(to, self) - c_num(from, self) + 1;