Index: openjpa-jdbc/src/main/java/org/apache/openjpa/jdbc/meta/ClassMapping.java
===================================================================
--- openjpa-jdbc/src/main/java/org/apache/openjpa/jdbc/meta/ClassMapping.java	(revision 564777)
+++ openjpa-jdbc/src/main/java/org/apache/openjpa/jdbc/meta/ClassMapping.java	(working copy)
@@ -30,6 +30,7 @@
 import java.util.Map;
 import java.util.Set;
 
+import org.apache.commons.lang.StringUtils;
 import org.apache.openjpa.jdbc.kernel.JDBCFetchConfiguration;
 import org.apache.openjpa.jdbc.kernel.JDBCStore;
 import org.apache.openjpa.jdbc.meta.strats.NoneClassStrategy;
@@ -189,7 +190,32 @@
             }
         }
         Object oid = ApplicationIds.fromPKValues(vals, cls);
-        if (!subs && oid instanceof OpenJPAId)
-            ((OpenJPAId) oid).setManagedInstanceType(cls.getDescribedType());
+        if (oid instanceof OpenJPAId) {
+            Class type = cls.getDescribedType();
+            if (!subs)
+                // non-polymorphic relations
+                ((OpenJPAId) oid).setManagedInstanceType(type);
+            else if (cls.getDiscriminator() != null
+                && !StringUtils.equals("none",
+                    cls.getDiscriminator().getStrategy().getAlias())) {
+                // for polymorphic relations,
+                // the type field in the oid was initially set to base type.
+                // If the discriminator value is preset in the current result,
+                // then the type field needs reset based on discriminator value.
+                // If the discriminator value is not present or not available,
+                // ignore any exceptions being thrown.
+                // The discriminator value can potentially be null in the 
+                // database because the mapping tool does not enforce the 
+                // discriminator column 'not null'.
+                // We can not prevent other non-jpa applications from inserting
+                // a null discriminator value.
+                res.startDataRequest(cls.getDiscriminator());
+                try {
+                    type = cls.getDiscriminator().getClass(store, cls, res);
+                    ((OpenJPAId) oid).setManagedInstanceType(type);
+                } catch (Exception e) {}
+                res.endDataRequest();  
+            } 
+        }
         return oid;
     }