--- pathauto.module	2005-05-24 00:57:30.000000000 +1000
+++ pathauto.undefined_separator.module	2005-06-04 01:21:58.000000000 +1000
@@ -160,7 +160,7 @@
   } else {
     $seppattern = '\\'.$separator;
   }
-  $output = preg_replace("/^$seppattern+|$seppattern+$/", "", $output);
+  $output = $seppattern ? preg_replace("/^$seppattern+|$seppattern+$/", "", $output) : $output;
   return $output;
 }