diff --git a/src/main/java/org/springframework/data/jpa/support/MergingPersistenceUnitManager.java b/src/main/java/org/springframework/data/jpa/support/MergingPersistenceUnitManager.java
index eae8cc1db..cab20a70d 100644
--- a/src/main/java/org/springframework/data/jpa/support/MergingPersistenceUnitManager.java
+++ b/src/main/java/org/springframework/data/jpa/support/MergingPersistenceUnitManager.java
@@ -61,29 +61,45 @@ public class MergingPersistenceUnitManager extends DefaultPersistenceUnitManager
 	 * (non-Javadoc)
 	 * @see org.springframework.orm.jpa.persistenceunit.DefaultPersistenceUnitManager#isPersistenceUnitOverrideAllowed()
 	 */
+	@Override
 	protected boolean isPersistenceUnitOverrideAllowed() {
 		return true;
 	}
 
 	void postProcessPersistenceUnitInfo(MutablePersistenceUnitInfo pui, PersistenceUnitInfo oldPui) {
 
-		for (URL url : oldPui.getJarFileUrls()) {
+		String persistenceUnitName = pui.getPersistenceUnitName();
 
-			// Add jar file url to PUI
+		for (URL url : oldPui.getJarFileUrls()) {
 			if (!pui.getJarFileUrls().contains(url)) {
-				log.debug("Adding {} to persistence units", url);
+				log.debug("Adding JAR file URL {} to persistence unit {}.", url, persistenceUnitName);
 				pui.addJarFileUrl(url);
 			}
 		}
 
 		for (String className : oldPui.getManagedClassNames()) {
-
 			if (!pui.getManagedClassNames().contains(className)) {
-				log.debug("Adding class {} to PersistenceUnit {}", className, pui.getPersistenceUnitName());
+				log.debug("Adding class {} to PersistenceUnit {}", className, persistenceUnitName);
 				pui.addManagedClassName(className);
 			}
 		}
 
-		pui.addJarFileUrl(oldPui.getPersistenceUnitRootUrl());
+		for (String mappingFileName : oldPui.getMappingFileNames()) {
+			if (!pui.getMappingFileNames().contains(mappingFileName)) {
+				log.debug("Adding mapping file to persistence unit {}.", mappingFileName, persistenceUnitName);
+				pui.addMappingFileName(mappingFileName);
+			}
+		}
+
+		URL newUrl = pui.getPersistenceUnitRootUrl();
+		URL oldUrl = oldPui.getPersistenceUnitRootUrl();
+
+		boolean hasNewRootUrl = newUrl != null;
+		boolean rootUrlsDiffer = hasNewRootUrl && !newUrl.equals(oldUrl);
+		boolean urlNotInJarUrls = hasNewRootUrl && !pui.getJarFileUrls().contains(oldUrl);
+
+		if (hasNewRootUrl && rootUrlsDiffer && urlNotInJarUrls) {
+			pui.addJarFileUrl(oldUrl);
+		}
 	}
 }
diff --git a/src/test/java/org/springframework/data/jpa/support/MergingPersistenceUnitManagerUnitTests.java b/src/test/java/org/springframework/data/jpa/support/MergingPersistenceUnitManagerUnitTests.java
index 30529be67..6ac893ef8 100644
--- a/src/test/java/org/springframework/data/jpa/support/MergingPersistenceUnitManagerUnitTests.java
+++ b/src/test/java/org/springframework/data/jpa/support/MergingPersistenceUnitManagerUnitTests.java
@@ -25,7 +25,6 @@ import java.util.Arrays;
 
 import javax.persistence.spi.PersistenceUnitInfo;
 
-import org.junit.Ignore;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.mockito.Mock;
@@ -59,11 +58,7 @@ public class MergingPersistenceUnitManagerUnitTests {
 		verify(newInfo).addJarFileUrl(jarFileUrl);
 	}
 
-	/**
-	 * @FIXME - Reactivate as soon as Spring 3.1.1 gets released
-	 */
 	@Test
-	@Ignore
 	public void mergesManagedClassesCorrectly() {
 
 		MergingPersistenceUnitManager manager = new MergingPersistenceUnitManager();
@@ -74,5 +69,54 @@ public class MergingPersistenceUnitManagerUnitTests {
 		PersistenceUnitInfo info = manager.obtainPersistenceUnitInfo("pu");
 		assertThat(info.getManagedClassNames().size(), is(2));
 		assertThat(info.getManagedClassNames(), hasItems(User.class.getName(), Role.class.getName()));
+
+		assertThat(info.getMappingFileNames().size(), is(2));
+		assertThat(info.getMappingFileNames(), hasItems("foo.xml", "bar.xml"));
+
+		System.out.println(info.getPersistenceUnitRootUrl());
+	}
+
+	@Test
+	public void addsOldPersistenceUnitRootUrlIfDifferentFromNewOne() throws MalformedURLException {
+
+		MutablePersistenceUnitInfo newInfo = new MutablePersistenceUnitInfo();
+		newInfo.setPersistenceUnitRootUrl(new URL("file:bar"));
+
+		when(oldInfo.getPersistenceUnitRootUrl()).thenReturn(new URL("file:/foo"));
+
+		MergingPersistenceUnitManager manager = new MergingPersistenceUnitManager();
+		manager.postProcessPersistenceUnitInfo(newInfo, oldInfo);
+
+		assertThat(newInfo.getJarFileUrls().size(), is(1));
+		assertThat(newInfo.getJarFileUrls(), hasItems(oldInfo.getPersistenceUnitRootUrl()));
+	}
+
+	@Test
+	public void doesNotAddNewPuRootUrlIfNull() throws MalformedURLException {
+
+		MutablePersistenceUnitInfo newInfo = new MutablePersistenceUnitInfo();
+
+		when(oldInfo.getPersistenceUnitRootUrl()).thenReturn(new URL("file:/foo"));
+
+		MergingPersistenceUnitManager manager = new MergingPersistenceUnitManager();
+		manager.postProcessPersistenceUnitInfo(newInfo, oldInfo);
+
+		assertThat(newInfo.getJarFileUrls().isEmpty(), is(true));
+	}
+
+	@Test
+	public void doesNotAddNewPuRootUrlIfAlreadyOnTheListOfJarFileUrls() throws MalformedURLException {
+
+		when(oldInfo.getPersistenceUnitRootUrl()).thenReturn(new URL("file:foo"));
+
+		MutablePersistenceUnitInfo newInfo = new MutablePersistenceUnitInfo();
+		newInfo.setPersistenceUnitRootUrl(new URL("file:bar"));
+		newInfo.addJarFileUrl(oldInfo.getPersistenceUnitRootUrl());
+
+		MergingPersistenceUnitManager manager = new MergingPersistenceUnitManager();
+		manager.postProcessPersistenceUnitInfo(newInfo, oldInfo);
+
+		assertThat(newInfo.getJarFileUrls().size(), is(1));
+		assertThat(newInfo.getJarFileUrls(), hasItems(oldInfo.getPersistenceUnitRootUrl()));
 	}
 }
diff --git a/src/test/resources/org/springframework/data/jpa/support/persistence.xml b/src/test/resources/org/springframework/data/jpa/support/persistence.xml
index 230d4bb2a..652dfa4de 100644
--- a/src/test/resources/org/springframework/data/jpa/support/persistence.xml
+++ b/src/test/resources/org/springframework/data/jpa/support/persistence.xml
@@ -1,6 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <persistence version="1.0" xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd">
 	<persistence-unit name="pu">
+		<mapping-file>foo.xml</mapping-file>
 		<class>org.springframework.data.jpa.domain.sample.User</class>
 	</persistence-unit>
 </persistence>
diff --git a/src/test/resources/org/springframework/data/jpa/support/persistence2.xml b/src/test/resources/org/springframework/data/jpa/support/persistence2.xml
index 756e2aa4a..b954da49f 100644
--- a/src/test/resources/org/springframework/data/jpa/support/persistence2.xml
+++ b/src/test/resources/org/springframework/data/jpa/support/persistence2.xml
@@ -1,6 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <persistence version="1.0" xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd">
 	<persistence-unit name="pu">
+		<mapping-file>bar.xml</mapping-file>
 		<class>org.springframework.data.jpa.domain.sample.Role</class>
 	</persistence-unit>
 </persistence>