diff --git a/fhem/FHEM/33_readingsGroup.pm b/fhem/FHEM/33_readingsGroup.pm
index a1451f99b..dc291c946 100644
--- a/fhem/FHEM/33_readingsGroup.pm
+++ b/fhem/FHEM/33_readingsGroup.pm
@@ -217,6 +217,8 @@ lookup2($$$$)
     $lookup = "" if( $@ );
   }
 
+  return $lookup if( !defined($lookup) );
+
   $lookup =~ s/\%DEVICE/$name/g;
   $lookup =~ s/\%READING/$reading/g;
   $lookup =~ s/\%VALUE/$value/g;