diff --git a/datastore_server/sourceTest/java/ch/systemsx/cisd/openbis/datastoreserver/systemtests/data-set-handler.py b/datastore_server/sourceTest/java/ch/systemsx/cisd/openbis/datastoreserver/systemtests/data-set-handler.py
index 21f8308bf8e51bf5466ea9c7ece6049958fbe2a0..ddb2efd802ea56d88a9ef00f045d4504879a0cc4 100644
--- a/datastore_server/sourceTest/java/ch/systemsx/cisd/openbis/datastoreserver/systemtests/data-set-handler.py
+++ b/datastore_server/sourceTest/java/ch/systemsx/cisd/openbis/datastoreserver/systemtests/data-set-handler.py
@@ -5,6 +5,6 @@ transaction = service.transaction(incoming)
 dataSet = transaction.createNewDataSet()
 exp = dataSet.getExperiment()
 samp = dataSet.getSample()
-if exp is None and samp is None:
-  raise IllegalArgumentException("No Experiment or Sample specified")
+if exp is None or samp is None:
+  raise IllegalArgumentException("data-set-handler.py: No Experiment or Sample specified")
 transaction.moveFile(incoming.getAbsolutePath(), dataSet)