diff --git a/includes/functions.php b/includes/functions.php
index 832d5c758..ca03a8eb4 100755
--- a/includes/functions.php
+++ b/includes/functions.php
@@ -127,6 +127,7 @@ function renamehost($id, $new, $source = 'console')
 {
   global $config;
 
+  ## FIXME does not check if destination exists!
   $host = dbFetchCell("SELECT `hostname` FROM `devices` WHERE `device_id` = ?", array($id));
   rename($config['rrd_dir']."/$host",$config['rrd_dir']."/$new");
   $return = dbUpdate(array('hostname' => $new), 'devices', 'device_id=?', array($id));
diff --git a/renamehost.php b/renamehost.php
index e949a7ffc..0abb5a8a6 100755
--- a/renamehost.php
+++ b/renamehost.php
@@ -13,8 +13,15 @@ if ($argv[1] && $argv[2])
   $id = getidbyname($host);
   if ($id)
   {
-    renamehost($id, $argv[2], 'console');
-    echo("Renamed $host\n");
+    $tohost = strtolower($argv[2]);
+    $toid = getidbyname($tohost);
+    if ($toid)
+    {
+      echo("NOT renamed. New hostname $tohost already exists.\n");
+    } else {
+      renamehost($id, $tohost, 'console');
+      echo("Renamed $host\n");
+    }
   } else {
     echo("Host doesn't exist!\n");
   }