importing a site backup made from pre-5.0 (pre user-rename) into 5.7 or later fails when there are content restriction set on any page

ERROR [Long running task: Importing data] [confluence.importexport.actions.ImportLongRunningTask] runInternal Failure during import
 -- url: /wiki/rest/oci/latest/import | userName: sysadmin
com.atlassian.confluence.importexport.ImportExportException: com.atlassian.confluence.importexport.ImportExportException: Unable to complete import: Error while importing backup: property does not exist: userName
	at com.atlassian.confluence.importexport.xmlimport.BackupImporter.importEntities(BackupImporter.java:429)
	at com.atlassian.confluence.importexport.xmlimport.BackupImporter.importEverything(BackupImporter.java:387)
	at com.atlassian.confluence.importexport.xmlimport.FileBackupImporter.importEverything(FileBackupImporter.java:154)
	at com.atlassian.confluence.importexport.xmlimport.BackupImporter$1.doInTransactionWithoutResult(BackupImporter.java:258)
	at org.springframework.transaction.support.TransactionCallbackWithoutResult.doInTransaction(TransactionCallbackWithoutResult.java:33)
	at com.atlassian.confluence.importexport.xmlimport.RestorePluginStateStoreTransactionCallbackDecorator.doInTransaction(RestorePluginStateStoreTransactionCallbackDecorator.java:50)
	at com.atlassian.confluence.importexport.xmlimport.RestoreBandanaValuesTransactionCallbackDecorator.doInTransaction(RestoreBandanaValuesTransactionCallbackDecorator.java:50)
	at org.springframework.transaction.support.TransactionTemplate.execute(TransactionTemplate.java:128)
	at com.atlassian.confluence.importexport.xmlimport.BackupImporter.doImportInternal(BackupImporter.java:210)
	at com.atlassian.confluence.importexport.Importer.doImport(Importer.java:77)
	at com.atlassian.confluence.importexport.DefaultImportExportManager.performImportInternal(DefaultImportExportManager.java:85)
	at com.atlassian.confluence.importexport.DefaultImportExportManager.performImport(DefaultImportExportManager.java:75)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:497)
	at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:307)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:182)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:149)
	at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:106)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
	at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204)
	at com.sun.proxy.$Proxy164.performImport(Unknown Source)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:497)
	at com.atlassian.plugin.util.ContextClassLoaderSettingInvocationHandler.invoke(ContextClassLoaderSettingInvocationHandler.java:26)
	at com.sun.proxy.$Proxy270.performImport(Unknown Source)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:497)
	at com.atlassian.plugin.osgi.bridge.external.HostComponentFactoryBean$DynamicServiceInvocationHandler.invoke(HostComponentFactoryBean.java:136)
	at com.sun.proxy.$Proxy270.performImport(Unknown Source)
	at com.atlassian.confluence.importexport.actions.ImportLongRunningTask.runInternal(ImportLongRunningTask.java:95)
	at com.atlassian.confluence.util.longrunning.ConfluenceAbstractLongRunningTask.run(ConfluenceAbstractLongRunningTask.java:27)
	at com.atlassian.ondemand.confluenceimporter.service.importer.OnDemandImportLongRunningTask.runInternal(OnDemandImportLongRunningTask.java:170)
	at com.atlassian.confluence.util.longrunning.ConfluenceAbstractLongRunningTask.run(ConfluenceAbstractLongRunningTask.java:27)
	at com.atlassian.confluence.util.longrunning.ManagedTask.run(ManagedTask.java:58)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at java.lang.Thread.run(Thread.java:745)
Caused by: com.atlassian.confluence.importexport.ImportExportException: Unable to complete import: Error while importing backup: property does not exist: userName
	at com.atlassian.confluence.importexport.xmlimport.DefaultXmlImporter.doImport(DefaultXmlImporter.java:77)
	at com.atlassian.confluence.importexport.xmlimport.BackupImporter.importEntities(BackupImporter.java:419)
	... 44 more
Caused by: org.xml.sax.SAXException: Error while importing backup: property does not exist: userName
net.sf.hibernate.MappingException: property does not exist: userName
	at com.atlassian.confluence.importexport.xmlimport.parser.BackupParser.endElement(BackupParser.java:55)
	at org.apache.xerces.parsers.AbstractSAXParser.endElement(Unknown Source)
	at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanEndElement(Unknown Source)
	at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl$FragmentContentDispatcher.dispatch(Unknown Source)
	at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanDocument(Unknown Source)
	at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source)
	at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source)
	at org.apache.xerces.parsers.XMLParser.parse(Unknown Source)
	at org.apache.xerces.parsers.AbstractSAXParser.parse(Unknown Source)
	at org.apache.xerces.jaxp.SAXParserImpl$JAXPSAXParser.parse(Unknown Source)
	at com.atlassian.security.xml.RestrictedXMLReader.parse(RestrictedXMLReader.java:103)
	at com.atlassian.confluence.importexport.xmlimport.DefaultXmlImporter.parseBackup(DefaultXmlImporter.java:103)
	at com.atlassian.confluence.importexport.xmlimport.DefaultXmlImporter.doImport(DefaultXmlImporter.java:61)
	... 45 more
Caused by: net.sf.hibernate.MappingException: property does not exist: userName
	at net.sf.hibernate.persister.AbstractEntityPersister.getPropertyType(AbstractEntityPersister.java:1133)
	at com.atlassian.confluence.importexport.xmlimport.persister.AbstractObjectPersister.getPrimitivePropertyValue(AbstractObjectPersister.java:45)
	at com.atlassian.confluence.importexport.xmlimport.persister.HibernateContentPermissionPersister.updateProperty(HibernateContentPermissionPersister.java:67)
	at com.atlassian.confluence.importexport.xmlimport.persister.HibernateContentPermissionPersister.persist(HibernateContentPermissionPersister.java:43)
	at com.atlassian.confluence.importexport.xmlimport.DefaultImportProcessor.persist(DefaultImportProcessor.java:47)
	at com.atlassian.confluence.importexport.xmlimport.DefaultImportProcessor.processObject(DefaultImportProcessor.java:37)
	at com.atlassian.confluence.importexport.xmlimport.parser.BackupParser.endElement(BackupParser.java:51)
	... 57 more