diff --git a/openbis/source/java/ch/systemsx/cisd/openbis/generic/shared/dto/ExperimentPE.java b/openbis/source/java/ch/systemsx/cisd/openbis/generic/shared/dto/ExperimentPE.java
index a3caf1bdcb1d629d46aa0a52c931a75515eedc1b..e4ccf1d65695ffc08997c80d1ee7fdd7649374d5 100644
--- a/openbis/source/java/ch/systemsx/cisd/openbis/generic/shared/dto/ExperimentPE.java
+++ b/openbis/source/java/ch/systemsx/cisd/openbis/generic/shared/dto/ExperimentPE.java
@@ -334,13 +334,6 @@ public class ExperimentPE implements IEntityPropertiesHolder<ExperimentPropertyP
             parent.getExperimentAttachments().remove(child);
         }
         child.setParentInternal(this);
-        // ensure that the collection is of the proper type - bean populator could set it to
-        // unmuttable empty list
-        if (getExperimentAttachments().size() == 0
-                && getExperimentAttachments() instanceof HashSet == false)
-        {
-            setExperimentAttachments(new ArrayList<AttachmentPE>());
-        }
         getExperimentAttachments().add(child);
     }