diff --git a/spring-batch-core/src/main/java/org/springframework/batch/core/repository/dao/MapJobExecutionDao.java b/spring-batch-core/src/main/java/org/springframework/batch/core/repository/dao/MapJobExecutionDao.java
index 138490e86..ae1464fc4 100644
--- a/spring-batch-core/src/main/java/org/springframework/batch/core/repository/dao/MapJobExecutionDao.java
+++ b/spring-batch-core/src/main/java/org/springframework/batch/core/repository/dao/MapJobExecutionDao.java
@@ -8,6 +8,7 @@ import java.util.List;
 import java.util.Map;
 import java.util.Set;
 
+import org.apache.commons.lang.SerializationUtils;
 import org.springframework.batch.core.JobExecution;
 import org.springframework.batch.core.JobInstance;
 import org.springframework.batch.support.transaction.TransactionAwareProxyFactory;
@@ -18,27 +19,32 @@ import org.springframework.util.Assert;
  */
 public class MapJobExecutionDao implements JobExecutionDao {
 
-	private static Map<Long, JobExecution> executionsById =  TransactionAwareProxyFactory.createTransactionalMap();
-	
+	private static Map<Long, JobExecution> executionsById = TransactionAwareProxyFactory.createTransactionalMap();
+
 	private static long currentId = 0;
 
 	public static void clear() {
 		executionsById.clear();
 	}
 
+	private static JobExecution copy(JobExecution original) {
+		JobExecution copy = (JobExecution) SerializationUtils.deserialize(SerializationUtils.serialize(original));
+		return copy;
+	}
+
 	public void saveJobExecution(JobExecution jobExecution) {
 		Assert.isTrue(jobExecution.getId() == null);
 		Long newId = new Long(currentId++);
 		jobExecution.setId(newId);
 		jobExecution.incrementVersion();
-		executionsById.put(newId, jobExecution);
+		executionsById.put(newId, copy(jobExecution));
 	}
 
 	public List<JobExecution> findJobExecutions(JobInstance jobInstance) {
 		List<JobExecution> executions = new ArrayList<JobExecution>();
 		for (JobExecution exec : executionsById.values()) {
 			if (exec.getJobInstance().equals(jobInstance)) {
-				executions.add(exec);
+				executions.add(copy(exec));
 			}
 		}
 		Collections.sort(executions, new Comparator<JobExecution>() {
@@ -47,9 +53,11 @@ public class MapJobExecutionDao implements JobExecutionDao {
 				long result = (e1.getId() - e2.getId());
 				if (result > 0) {
 					return -1;
-				} else if (result < 0) {
+				}
+				else if (result < 0) {
 					return 1;
-				} else {
+				}
+				else {
 					return 0;
 				}
 			}
@@ -62,7 +70,7 @@ public class MapJobExecutionDao implements JobExecutionDao {
 		Assert.notNull(id, "JobExecution is expected to have an id (should be saved already)");
 		Assert.notNull(executionsById.get(id), "JobExecution must already be saved");
 		jobExecution.incrementVersion();
-		executionsById.put(id, jobExecution);
+		executionsById.put(id, copy(jobExecution));
 	}
 
 	public JobExecution getLastJobExecution(JobInstance jobInstance) {
@@ -78,11 +86,14 @@ public class MapJobExecutionDao implements JobExecutionDao {
 				lastExec = exec;
 			}
 		}
-		return lastExec;
+		return copy(lastExec);
 	}
 
-	/* (non-Javadoc)
-	 * @see org.springframework.batch.core.repository.dao.JobExecutionDao#findRunningJobExecutions(java.lang.String)
+	/*
+	 * (non-Javadoc)
+	 * 
+	 * @seeorg.springframework.batch.core.repository.dao.JobExecutionDao#
+	 * findRunningJobExecutions(java.lang.String)
 	 */
 	public Set<JobExecution> findRunningJobExecutions(String jobName) {
 		Set<JobExecution> result = new HashSet<JobExecution>();
@@ -90,16 +101,20 @@ public class MapJobExecutionDao implements JobExecutionDao {
 			if (!exec.getJobInstance().getJobName().equals(jobName) || !exec.isRunning()) {
 				continue;
 			}
-			result.add(exec);
+			result.add(copy(exec));
 		}
 		return result;
 	}
 
-	/* (non-Javadoc)
-	 * @see org.springframework.batch.core.repository.dao.JobExecutionDao#getJobExecution(java.lang.Long)
+	/*
+	 * (non-Javadoc)
+	 * 
+	 * @see
+	 * org.springframework.batch.core.repository.dao.JobExecutionDao#getJobExecution
+	 * (java.lang.Long)
 	 */
 	public JobExecution getJobExecution(Long executionId) {
-		return executionsById.get(executionId);
+		return copy(executionsById.get(executionId));
 	}
 
 	public void synchronizeStatus(JobExecution jobExecution) {
diff --git a/spring-batch-core/src/test/java/org/springframework/batch/core/repository/dao/MapJobExecutionDaoTests.java b/spring-batch-core/src/test/java/org/springframework/batch/core/repository/dao/MapJobExecutionDaoTests.java
index a731f003e..6015ed0ee 100644
--- a/spring-batch-core/src/test/java/org/springframework/batch/core/repository/dao/MapJobExecutionDaoTests.java
+++ b/spring-batch-core/src/test/java/org/springframework/batch/core/repository/dao/MapJobExecutionDaoTests.java
@@ -1,7 +1,15 @@
 package org.springframework.batch.core.repository.dao;
 
+import java.util.Date;
+
+import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.junit.internal.runners.JUnit4ClassRunner;
+import org.springframework.batch.core.JobExecution;
+import org.springframework.batch.core.JobInstance;
+import org.springframework.batch.core.JobParameters;
+
+import static org.junit.Assert.*;
 
 @RunWith(JUnit4ClassRunner.class)
 public class MapJobExecutionDaoTests extends AbstractJobExecutionDaoTests {
@@ -12,4 +20,21 @@ public class MapJobExecutionDaoTests extends AbstractJobExecutionDaoTests {
 		return new MapJobExecutionDao();
 	}
 
+	/**
+	 * Modifications to saved entity do not affect the persisted object.
+	 */
+	@Test
+	public void testPersistentCopy() {
+		JobExecutionDao tested = new MapJobExecutionDao();
+		JobExecution jobExecution = new JobExecution(new JobInstance((long) 1, new JobParameters(), "mapJob"));
+		
+		assertNull(jobExecution.getStartTime());
+		tested.saveJobExecution(jobExecution);
+		jobExecution.setStartTime(new Date());
+		
+		JobExecution retrieved = tested.getJobExecution(jobExecution.getId());
+		assertNull(retrieved.getStartTime());
+		
+	}
+
 }