diff --git a/fhem/CHANGED b/fhem/CHANGED
index f5186790b..8a69bd57d 100644
--- a/fhem/CHANGED
+++ b/fhem/CHANGED
@@ -24,6 +24,7 @@
              loading automatically. A restart is required now! (M. Fischer)
   - feature: 98_update.pm saves the statefile before an update (M. Fischer)
   - feature: FHEMWEB longpoll reconnect (Matthias)
+  - bugfix:  rename may overwrite other devices
 
 - 2012-10-28 (5.3)
   - feature: added functions trim, ltrim, rtrim, UntoggleDirect,
diff --git a/fhem/fhem.pl b/fhem/fhem.pl
index 2cc034ac4..c10288cc3 100755
--- a/fhem/fhem.pl
+++ b/fhem/fhem.pl
@@ -1548,6 +1548,7 @@ CommandRename($$)
   $old = "''" if(!defined($old));
 
   return "Please define $old first" if(!defined($defs{$old}));
+  return "$new already defined" if(defined($defs{$new}));
   return "Invalid characters in name (not A-Za-z0-9.:_): $new"
                         if($new !~ m/^[a-z0-9.:_]*$/i);
   return "Cannot rename global" if($old eq "global");