diff --git a/doctrine-orm/Doctrine/ORM/Persisters/SingleTablePersister.php b/doctrine-orm/Doctrine/ORM/Persisters/SingleTablePersister.php
index f910a8e..78b27cb 100644
--- a/doctrine-orm/Doctrine/ORM/Persisters/SingleTablePersister.php
+++ b/doctrine-orm/Doctrine/ORM/Persisters/SingleTablePersister.php
@@ -41,6 +41,15 @@ class SingleTablePersister extends AbstractEntityInheritancePersister
     /** {@inheritdoc} */
     protected function _getSelectColumnListSQL()
     {
+        /** @see BasicEntityPersister::_getSelectColumnListSQL() */
+        if ($this->_selectColumnListSql !== null) {
+            return $this->_selectColumnListSql;
+        }
+
+        #####
+        #####
+        #####
+
         $columnList = parent::_getSelectColumnListSQL();
 
         // Append discriminator column
@@ -74,7 +83,13 @@ class SingleTablePersister extends AbstractEntityInheritancePersister
             }
         }
 
-        return $columnList;
+        #####
+        #####
+        #####
+
+        /** @see BasicEntityPersister::_getSelectColumnListSQL() */
+        $this->_selectColumnListSql = $columnList;
+        return $this->_selectColumnListSql;
     }
 
     /** {@inheritdoc} */