diff --git a/fhem/fhem.pl b/fhem/fhem.pl
index 382cfbaf5..52048c738 100755
--- a/fhem/fhem.pl
+++ b/fhem/fhem.pl
@@ -4884,8 +4884,8 @@ readingsBulkUpdate($$$@)
       } else {
         require "TimeSeries.pm";
         $ts = TimeSeries->new( { method => $method, 
-                  autoreset=>(looks_like_number($duration) ? $duration:undef),
-                  holdTime =>(looks_like_number($holdTime) ? $holdTime:undef)});
+                  autoreset => $duration,
+                  holdTime => $holdTime } );
         $readings->{".ts"}= $ts;
         # access from command line:
         # { $defs{"myClient"}{READINGS}{"myValue"}{".ts"}{max} }