diff --git a/hibernate-core/src/main/java/org/hibernate/type/ManyToOneType.java b/hibernate-core/src/main/java/org/hibernate/type/ManyToOneType.java
index 1bbdaf31de..a1a1634231 100644
--- a/hibernate-core/src/main/java/org/hibernate/type/ManyToOneType.java
+++ b/hibernate-core/src/main/java/org/hibernate/type/ManyToOneType.java
@@ -189,15 +189,18 @@ public class ManyToOneType extends EntityType {
 			boolean[] checkable,
 			SharedSessionContractImplementor session) throws HibernateException {
 		if ( current == null ) {
-			return old!=null;
+			return old != null;
 		}
 		if ( old == null ) {
 			// we already know current is not null...
 			return true;
 		}
+
+		assert current.getClass().isAssignableFrom( old.getClass() );
+
 		// the ids are fully resolved, so compare them with isDirty(), not isModified()
 		return getIdentifierOrUniqueKeyType( session.getFactory() )
-				.isDirty( old, getIdentifier( current, session ), session );
+				.isDirty( getIdentifier( old, session ), getIdentifier( current, session ), session );
 	}
 
 	@Override
diff --git a/hibernate-core/src/main/java/org/hibernate/type/OneToOneType.java b/hibernate-core/src/main/java/org/hibernate/type/OneToOneType.java
index a03f47bee9..83f4bd527b 100644
--- a/hibernate-core/src/main/java/org/hibernate/type/OneToOneType.java
+++ b/hibernate-core/src/main/java/org/hibernate/type/OneToOneType.java
@@ -121,10 +121,8 @@ public class OneToOneType extends EntityType {
 			return false;
 		}
 
-		Object oldid = getIdentifier( old, session );
-		Object newid = getIdentifier( current, session );
-
-		return getIdentifierType( session ).isDirty( oldid, newid, session );
+		return getIdentifierType( session )
+				.isDirty( getIdentifier( old, session ), getIdentifier( current, session ), session );
 	}
 
 	@Override