XML import doesn't correctly import assignments with multiple values

To reproduce:

Using GSH:

grouperSession = GrouperSession.startRootSession();
Stem stem = StemFinder.findByName(grouperSession, "etc", true);
Group groupA = stem.addChildGroup("groupA", "groupA");
AttributeDef attributeDef = stem.addChildAttributeDef("attributeDef", AttributeDefType.attr);
attributeDef.setAssignToGroup(true);
attributeDef.setValueType(AttributeDefValueType.string);
attributeDef.setMultiValued(true);
attributeDef.store();
AttributeDefName attributeDefName = stem.addChildAttributeDefName(attributeDef, "attribute", "attribute");

groupA.getAttributeValueDelegate().addValue(attributeDefName.getName(), "value1");
groupA.getAttributeValueDelegate().addValue(attributeDefName.getName(), "value2");

$ ./bin/gsh.sh -xmlexport /tmp/export

File contains the following:

<attributeAssignValues>
<XmlExportAttributeAssignValue><attributeAssignId>ae7447cccd474800b1420e38aaa0a23d</attributeAssignId><contextId>bd181141572f4230bd5e57d58b8f1a9a</contextId><createTime>2013/12/26 15:25:25.887</createTime><hibernateVersionNumber>0</hibernateVersionNumber><modifierTime>2013/12/26 15:25:25.887</modifierTime><uuid>00d4da3674ea4e9e92a926a941d85c79</uuid><valueString>value1</valueString></XmlExportAttributeAssignValue>
<XmlExportAttributeAssignValue><attributeAssignId>ae7447cccd474800b1420e38aaa0a23d</attributeAssignId><contextId>33adc42c5a3d4dd396f913e921d73228</contextId><createTime>2013/12/26 15:25:25.914</createTime><hibernateVersionNumber>0</hibernateVersionNumber><modifierTime>2013/12/26 15:25:25.914</modifierTime><uuid>b833ecf7c19c45c0a3e5bc4e593e66ac</uuid><valueString>value2</valueString></XmlExportAttributeAssignValue>
</attributeAssignValues>

Clear the db, import the file, only "value2" is present in the db. Log indicates that the second value overwrote the first instead of adding a new row:

Insert: AttributeAssignValue: 00d4da3674ea4e9e92a926a941d85c79
Update: AttributeAssignValue: 00d4da3674ea4e9e92a926a941d85c79