diff --git a/lib/Doctrine/ORM/Persisters/SingleTablePersister.php b/lib/Doctrine/ORM/Persisters/SingleTablePersister.php
index 3f7574cba..ddeb1b108 100644
--- a/lib/Doctrine/ORM/Persisters/SingleTablePersister.php
+++ b/lib/Doctrine/ORM/Persisters/SingleTablePersister.php
@@ -100,7 +100,11 @@ class SingleTablePersister extends AbstractEntityInheritancePersister
 
         // Append discriminator condition
         if ($conditionSql) $conditionSql .= ' AND ';
-        $values = array($this->_conn->quote($this->_class->discriminatorValue));
+        $values = array();
+        if ($this->_class->discriminatorValue !== null) { // discriminators can be 0
+            $values[] = $this->_conn->quote($this->_class->discriminatorValue);
+        }
+
         $discrValues = array_flip($this->_class->discriminatorMap);
         foreach ($this->_class->subClasses as $subclassName) {
             $values[] = $this->_conn->quote($discrValues[$subclassName]);
diff --git a/lib/Doctrine/ORM/Query/SqlWalker.php b/lib/Doctrine/ORM/Query/SqlWalker.php
index 289e0200d..323599927 100644
--- a/lib/Doctrine/ORM/Query/SqlWalker.php
+++ b/lib/Doctrine/ORM/Query/SqlWalker.php
@@ -320,7 +320,10 @@ class SqlWalker implements TreeWalker
 
             if ($class->isInheritanceTypeSingleTable()) {
                 $conn = $this->_em->getConnection();
-                $values = array($conn->quote($class->discriminatorValue));
+                $values = array();
+                if ($class->discriminatorValue !== null) { // discrimnators can be 0
+                    $values[] = $conn->quote($class->discriminatorValue);
+                }
 
                 foreach ($class->subClasses as $subclassName) {
                     $values[] = $conn->quote($this->_em->getClassMetadata($subclassName)->discriminatorValue);
diff --git a/tests/Doctrine/Tests/ORM/Functional/SingleTableInheritanceTest.php b/tests/Doctrine/Tests/ORM/Functional/SingleTableInheritanceTest.php
index 84705831c..b2bd382c6 100644
--- a/tests/Doctrine/Tests/ORM/Functional/SingleTableInheritanceTest.php
+++ b/tests/Doctrine/Tests/ORM/Functional/SingleTableInheritanceTest.php
@@ -219,9 +219,13 @@ class SingleTableInheritanceTest extends \Doctrine\Tests\OrmFunctionalTestCase
 
         $contracts = $this->_em->createQuery('SELECT c FROM Doctrine\Tests\Models\Company\CompanyContract c ORDER BY c.id')->getScalarResult();
 
-        $this->assertEquals('fix', $contracts[0]['c_discr']);
-        $this->assertEquals('flexible', $contracts[1]['c_discr']);
-        $this->assertEquals('flexultra', $contracts[2]['c_discr']);
+        $discrValues = \array_map(function($a) {
+            return $a['c_discr'];
+        }, $contracts);
+
+        sort($discrValues);
+
+        $this->assertEquals(array('fix', 'flexible', 'flexultra'), $discrValues);
     }
 
     public function testQueryChildClassWithCondition()