diff --git a/openbis/source/java/ch/systemsx/cisd/openbis/generic/shared/dto/AttachmentHolderPE.java b/openbis/source/java/ch/systemsx/cisd/openbis/generic/shared/dto/AttachmentHolderPE.java
index 06b9bba45a76763a0d855e2ed67554b859bf560c..dae74bcebf63f35a03530b1b8c47e9d5fb0d4150 100644
--- a/openbis/source/java/ch/systemsx/cisd/openbis/generic/shared/dto/AttachmentHolderPE.java
+++ b/openbis/source/java/ch/systemsx/cisd/openbis/generic/shared/dto/AttachmentHolderPE.java
@@ -63,6 +63,7 @@ public abstract class AttachmentHolderPE implements Serializable
     // Abstract methods
     //
     @Transient
+    @Private
     abstract public Set<AttachmentPE> getInternalAttachments();
 
     @Transient