diff --git a/IP.pm b/IP.pm
index 4822f28..e0cd544 100644
--- a/IP.pm
+++ b/IP.pm
@@ -426,6 +426,7 @@
   my @low;
   my @up;
   return ([],[]) if $_[0] == $_[1];
+  return ([$_[0]],[]) unless $_[1]->within($_[0]);
   my ($s1,$s2) = $_[0]->split($_[0]->masklen+1);
   while ($s1 != $_[1] && $s2 != $_[1]) {
     if ($_[1]->within($s1)) {