diff --git a/GeneticsCore/src/org/labkey/GeneticsCore/mhc/MhcTaskRef.java b/GeneticsCore/src/org/labkey/GeneticsCore/mhc/MhcTaskRef.java
index d8fc5b97f..50eb4196a 100644
--- a/GeneticsCore/src/org/labkey/GeneticsCore/mhc/MhcTaskRef.java
+++ b/GeneticsCore/src/org/labkey/GeneticsCore/mhc/MhcTaskRef.java
@@ -137,7 +137,7 @@ private void processSubject(PipelineJob job, String subject) throws PipelineJobE
             {
                 job.getLogger().info("deleting existing rows: " + toDelete.size());
                 QueryUpdateService qus = mhcData.getUpdateService();
-                qus.setBulkLoad(true);
+                qus.setBulkLoad(false); //preserve audit trail
                 qus.deleteRows(job.getUser(), getTargetContainer(job), toDelete, null, null);
             }
             catch (InvalidKeyException | BatchValidationException | QueryUpdateServiceException | SQLException e)