diff --git a/fhem/FHEM/01_FHEMWEB.pm b/fhem/FHEM/01_FHEMWEB.pm
index 89c29d832..34582b8ed 100755
--- a/fhem/FHEM/01_FHEMWEB.pm
+++ b/fhem/FHEM/01_FHEMWEB.pm
@@ -931,8 +931,7 @@ FW_roomIdx(\@$)
   my ($index) = grep { $arr->[$_] =~ /^$v$/ } 0..$#$arr;
 
   return "9999-$v" if( !defined($index) );
-
-  return $index;
+  return sprintf( "%03i", $index );
 }