diff --git a/hibernate-core/src/main/java/org/hibernate/persister/entity/SingleTableEntityPersister.java b/hibernate-core/src/main/java/org/hibernate/persister/entity/SingleTableEntityPersister.java
index e66822ed56..d5f62787c6 100644
--- a/hibernate-core/src/main/java/org/hibernate/persister/entity/SingleTableEntityPersister.java
+++ b/hibernate-core/src/main/java/org/hibernate/persister/entity/SingleTableEntityPersister.java
@@ -410,7 +410,7 @@ public class SingleTableEntityPersister extends AbstractEntityPersister {
 		subclassClosure = new String[subclassSpan];
 		subclassClosure[0] = getEntityName();
 		if ( persistentClass.isPolymorphic() ) {
-			subclassesByDiscriminatorValue.put( discriminatorValue, getEntityName() );
+			addSubclassByDiscriminatorValue( discriminatorValue, getEntityName() );
 		}
 
 		// SUBCLASSES
@@ -421,15 +421,15 @@ public class SingleTableEntityPersister extends AbstractEntityPersister {
 				Subclass sc = (Subclass) iter.next();
 				subclassClosure[k++] = sc.getEntityName();
 				if ( sc.isDiscriminatorValueNull() ) {
-					subclassesByDiscriminatorValue.put( NULL_DISCRIMINATOR, sc.getEntityName() );
+					addSubclassByDiscriminatorValue( NULL_DISCRIMINATOR, sc.getEntityName() );
 				}
 				else if ( sc.isDiscriminatorValueNotNull() ) {
-					subclassesByDiscriminatorValue.put( NOT_NULL_DISCRIMINATOR, sc.getEntityName() );
+					addSubclassByDiscriminatorValue( NOT_NULL_DISCRIMINATOR, sc.getEntityName() );
 				}
 				else {
 					try {
 						DiscriminatorType dtype = (DiscriminatorType) discriminatorType;
-						subclassesByDiscriminatorValue.put(
+						addSubclassByDiscriminatorValue(
 							dtype.stringToObject( sc.getDiscriminatorValue() ),
 							sc.getEntityName()
 						);
@@ -452,6 +452,16 @@ public class SingleTableEntityPersister extends AbstractEntityPersister {
 
 	}
 
+	private void addSubclassByDiscriminatorValue(Object discriminatorValue, String entityName) {
+		String mappedEntityName = (String) subclassesByDiscriminatorValue.put( discriminatorValue, entityName );
+		if ( mappedEntityName != null ) {
+			throw new MappingException(
+					"Entities [" + entityName + "] and [" + mappedEntityName
+							+ "] are mapped with the same discriminator value '" + discriminatorValue + "'."
+			);
+		}
+	}
+
 	public SingleTableEntityPersister(
 			final EntityBinding entityBinding,
 			final EntityRegionAccessStrategy cacheAccessStrategy,
@@ -674,7 +684,7 @@ public class SingleTableEntityPersister extends AbstractEntityPersister {
 		subclassClosure = new String[subclassSpan];
 		subclassClosure[0] = getEntityName();
 		if ( entityBinding.isPolymorphic() ) {
-			subclassesByDiscriminatorValue.put( discriminatorValue, getEntityName() );
+			addSubclassByDiscriminatorValue( discriminatorValue, getEntityName() );
 		}
 
 		// SUBCLASSES
@@ -683,15 +693,15 @@ public class SingleTableEntityPersister extends AbstractEntityPersister {
 			for ( EntityBinding subEntityBinding : entityBinding.getPostOrderSubEntityBindingClosure() ) {
 				subclassClosure[k++] = subEntityBinding.getEntity().getName();
 				if ( subEntityBinding.isDiscriminatorMatchValueNull() ) {
-					subclassesByDiscriminatorValue.put( NULL_DISCRIMINATOR, subEntityBinding.getEntity().getName() );
+					addSubclassByDiscriminatorValue( NULL_DISCRIMINATOR, subEntityBinding.getEntity().getName() );
 				}
 				else if ( subEntityBinding.isDiscriminatorMatchValueNotNull() ) {
-					subclassesByDiscriminatorValue.put( NOT_NULL_DISCRIMINATOR, subEntityBinding.getEntity().getName() );
+					addSubclassByDiscriminatorValue( NOT_NULL_DISCRIMINATOR, subEntityBinding.getEntity().getName() );
 				}
 				else {
 					try {
 						DiscriminatorType dtype = (DiscriminatorType) discriminatorType;
-						subclassesByDiscriminatorValue.put(
+						addSubclassByDiscriminatorValue(
 							dtype.stringToObject( subEntityBinding.getDiscriminatorMatchValue() ),
 							subEntityBinding.getEntity().getName()
 						);
diff --git a/hibernate-core/src/test/java/org/hibernate/test/annotations/inheritance/singletable/DuplicatedDiscriminatorValueTest.java b/hibernate-core/src/test/java/org/hibernate/test/annotations/inheritance/singletable/DuplicatedDiscriminatorValueTest.java
new file mode 100644
index 0000000000..fc68f75034
--- /dev/null
+++ b/hibernate-core/src/test/java/org/hibernate/test/annotations/inheritance/singletable/DuplicatedDiscriminatorValueTest.java
@@ -0,0 +1,91 @@
+package org.hibernate.test.annotations.inheritance.singletable;
+
+import javax.persistence.DiscriminatorColumn;
+import javax.persistence.DiscriminatorValue;
+import javax.persistence.Entity;
+import javax.persistence.GeneratedValue;
+import javax.persistence.Id;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import org.hibernate.MappingException;
+import org.hibernate.SessionFactory;
+import org.hibernate.cfg.Configuration;
+import org.hibernate.service.ServiceRegistry;
+import org.hibernate.testing.ServiceRegistryBuilder;
+import org.hibernate.testing.TestForIssue;
+import org.hibernate.testing.junit4.BaseUnitTestCase;
+
+/**
+ * @author Lukasz Antoniak (lukasz dot antoniak at gmail dot com)
+ */
+@TestForIssue( jiraKey = "HHH-7214" )
+public class DuplicatedDiscriminatorValueTest extends BaseUnitTestCase {
+	private static final String DISCRIMINATOR_VALUE = "D";
+
+	@Test
+	public void testDuplicatedDiscriminatorValueSameHierarchy() {
+		try {
+			tryBuildingSessionFactory( Building.class, Building1.class, Building2.class );
+			Assert.fail( MappingException.class.getName() + " expected when two subclasses are mapped with the same discriminator value." );
+		}
+		catch ( MappingException e ) {
+			final String errorMsg = e.getCause().getMessage();
+			// Check if error message contains descriptive information.
+			Assert.assertTrue( errorMsg.contains( Building1.class.getName() ) );
+			Assert.assertTrue( errorMsg.contains( Building2.class.getName() ) );
+			Assert.assertTrue( errorMsg.contains( "discriminator value '" + DISCRIMINATOR_VALUE + "'." ) );
+		}
+	}
+
+	@Test
+	public void testDuplicatedDiscriminatorValueDifferentHierarchy() {
+		tryBuildingSessionFactory( Building.class, Building1.class, Furniture.class, Chair.class );
+	}
+
+	private void tryBuildingSessionFactory(Class... annotatedClasses) {
+		Configuration cfg = new Configuration();
+		for ( Class annotatedClass : annotatedClasses ) {
+			cfg.addAnnotatedClass( annotatedClass );
+		}
+		ServiceRegistry serviceRegistry = null;
+		SessionFactory sessionFactory = null;
+		try {
+			serviceRegistry = ServiceRegistryBuilder.buildServiceRegistry( cfg.getProperties() );
+			sessionFactory = cfg.buildSessionFactory( serviceRegistry );
+		}
+		finally {
+			if ( sessionFactory != null ) {
+				sessionFactory.close();
+			}
+			if ( serviceRegistry != null ) {
+				ServiceRegistryBuilder.destroy( serviceRegistry );
+			}
+		}
+	}
+
+	@Entity
+	@DiscriminatorValue(DISCRIMINATOR_VALUE) // Duplicated discriminator value in single hierarchy.
+	private static class Building1 extends Building {
+	}
+
+	@Entity
+	@DiscriminatorValue(DISCRIMINATOR_VALUE) // Duplicated discriminator value in single hierarchy.
+	private static class Building2 extends Building {
+	}
+
+	@Entity
+	@DiscriminatorColumn(name = "entity_type")
+	@DiscriminatorValue("F")
+	private static class Furniture {
+		@Id
+		@GeneratedValue
+		private Integer id;
+	}
+
+	@Entity
+	@DiscriminatorValue(DISCRIMINATOR_VALUE) // Duplicated discriminator value in different hierarchy.
+	private static class Chair extends Furniture {
+	}
+}