diff --git a/FHEM/73_GasCalculator.pm b/FHEM/73_GasCalculator.pm
index a66f6d921..9e577a53c 100644
--- a/FHEM/73_GasCalculator.pm
+++ b/FHEM/73_GasCalculator.pm
@@ -731,13 +731,16 @@ sub GasCalculator_Notify($$)
 		Log3 $GasCalcName, 5, $GasCalcName. " : GasCalculator End_________________________________________________________________________________________________________________________________";
 	}
 	
-	### Update list of available readings
-	%GasCalculator_gets = %{$GasCalcDev->{READINGS}};
-	%GasCalculator_sets = %{$GasCalcDev->{READINGS}};
-
-	### Create Log entries for debugging
-	Log3 $GasCalcName, 5, $GasCalcName. " : GasCalculator - notify x_sets list: " . join(" ", (keys %GasCalculator_sets));
+	### If readings exist already, update list of available readings
+	if($GasCalcDev->{READINGS}) 
+	{
+		### Copy readings in list of available "gets" and "sets"
+		%GasCalculator_gets = %{$GasCalcDev->{READINGS}};
+		%GasCalculator_sets = %{$GasCalcDev->{READINGS}};
 
+		### Create Log entries for debugging
+		Log3 $GasCalcName, 5, $GasCalcName. " : GasCalculator - notify x_sets list: " . join(" ", (keys %GasCalculator_sets));
+	}
 	
 	return undef;
 }