diff --git a/src/main/java/org/springframework/data/jpa/provider/JpaClassUtils.java b/src/main/java/org/springframework/data/jpa/provider/JpaClassUtils.java
index 7b2ac83ce..54e023b4c 100644
--- a/src/main/java/org/springframework/data/jpa/provider/JpaClassUtils.java
+++ b/src/main/java/org/springframework/data/jpa/provider/JpaClassUtils.java
@@ -43,7 +43,11 @@ abstract class JpaClassUtils {
 	 * @return
 	 */
 	public static boolean isEntityManagerOfType(EntityManager em, String type) {
-		return isOfType(em, type, em.getDelegate().getClass().getClassLoader());
+		Object delegate = em.getDelegate();
+		if (delegate instanceof EntityManager) {
+			em = (EntityManager) delegate;
+		}
+		return isOfType(em, type, delegate.getClass().getClassLoader());
 	}
 
 	public static boolean isMetamodelOfType(Metamodel metamodel, String type) {
diff --git a/src/main/java/org/springframework/data/jpa/provider/PersistenceProvider.java b/src/main/java/org/springframework/data/jpa/provider/PersistenceProvider.java
index ee4f6d19a..9bb7f00e3 100644
--- a/src/main/java/org/springframework/data/jpa/provider/PersistenceProvider.java
+++ b/src/main/java/org/springframework/data/jpa/provider/PersistenceProvider.java
@@ -44,6 +44,7 @@ import org.springframework.util.ConcurrentReferenceHashMap;
  * @author Oliver Gierke
  * @author Thomas Darimont
  * @author Mark Paluch
+ * @author Jens Schauder
  */
 public enum PersistenceProvider implements QueryExtractor, ProxyIdAccessor {
 
@@ -224,7 +225,7 @@ public enum PersistenceProvider implements QueryExtractor, ProxyIdAccessor {
 		String OPENJPA_JPA_METAMODEL_TYPE = "org.apache.openjpa.persistence.meta.MetamodelImpl";
 	}
 
-	private static ConcurrentReferenceHashMap<Class<?>, PersistenceProvider> CACHE = new ConcurrentReferenceHashMap<Class<?>, PersistenceProvider>();
+	static ConcurrentReferenceHashMap<Class<?>, PersistenceProvider> CACHE = new ConcurrentReferenceHashMap<Class<?>, PersistenceProvider>();
 
 	private final Iterable<String> entityManagerClassNames;
 	private final Iterable<String> metamodelClassNames;
diff --git a/src/test/java/org/springframework/data/jpa/provider/PersistenceProviderUnitTests.java b/src/test/java/org/springframework/data/jpa/provider/PersistenceProviderUnitTests.java
index 78fcdfb58..62b4419f9 100644
--- a/src/test/java/org/springframework/data/jpa/provider/PersistenceProviderUnitTests.java
+++ b/src/test/java/org/springframework/data/jpa/provider/PersistenceProviderUnitTests.java
@@ -40,6 +40,7 @@ import org.springframework.util.ClassUtils;
  * 
  * @author Thomas Darimont
  * @author Oliver Gierke
+ * @author Jens Schauder
  */
 public class PersistenceProviderUnitTests {
 
@@ -47,6 +48,9 @@ public class PersistenceProviderUnitTests {
 
 	@Before
 	public void setup() {
+
+		PersistenceProvider.CACHE.clear();
+
 		this.shadowingClassLoader = new ShadowingClassLoader(getClass().getClassLoader());
 	}
 
@@ -80,12 +84,25 @@ public class PersistenceProviderUnitTests {
 		assertThat(fromEntityManager(em), is(HIBERNATE));
 	}
 
+	@Test // DATAJPA-1379
+	public void detectsProviderFromProxiedEntityManager() throws Exception {
+
+		shadowingClassLoader.excludePackage("org.eclipse.persistence.jpa");
+
+		EntityManager em = mockProviderSpecificEntityManagerInterface(ECLIPSELINK_ENTITY_MANAGER_INTERFACE);
+
+		EntityManager emProxy = Mockito.mock(EntityManager.class);
+		Mockito.when(emProxy.getDelegate()).thenReturn(em);
+
+		assertThat(fromEntityManager(emProxy), is(ECLIPSELINK));
+	}
+
 	private EntityManager mockProviderSpecificEntityManagerInterface(String interfaceName) throws ClassNotFoundException {
 
 		Class<?> providerSpecificEntityManagerInterface = InterfaceGenerator.generate(interfaceName, shadowingClassLoader,
 				EntityManager.class);
 
-		EntityManager em = EntityManager.class.cast(Mockito.mock(providerSpecificEntityManagerInterface));
+		EntityManager em = (EntityManager) Mockito.mock(providerSpecificEntityManagerInterface);
 		Mockito.when(em.getDelegate()).thenReturn(em); // delegate is used to determine the classloader of the provider
 																										// specific interface, therefore we return the proxied
 																										// EntityManager.