diff --git a/openbis/source/java/ch/systemsx/cisd/openbis/generic/server/business/bo/AbstractSampleBusinessObject.java b/openbis/source/java/ch/systemsx/cisd/openbis/generic/server/business/bo/AbstractSampleBusinessObject.java
index 8568f69ef846b1d82f307c420ef92ab361c89af0..9075be64c61ba598da4dcb9cf3f303b8aa3cbd4e 100644
--- a/openbis/source/java/ch/systemsx/cisd/openbis/generic/server/business/bo/AbstractSampleBusinessObject.java
+++ b/openbis/source/java/ch/systemsx/cisd/openbis/generic/server/business/bo/AbstractSampleBusinessObject.java
@@ -220,7 +220,7 @@ abstract class AbstractSampleBusinessObject extends AbstractSampleIdentifierBusi
             final SampleIdentifier sampleIdentifier)
     {
         SamplePE sample = tryGetValidSample(parentIdentifierOrNull, sampleIdentifier);
-        if (sample.getContainer() != null)
+        if (sample != null && sample.getContainer() != null)
         {
             throw UserFailureException.fromTemplate(
                     "Cannot register sample '%s': parent '%s' is part of another sample.",