diff --git a/lib/Doctrine/ORM/Id/AssignedGenerator.php b/lib/Doctrine/ORM/Id/AssignedGenerator.php
index 3ad2cbff7..9bdaa0efc 100644
--- a/lib/Doctrine/ORM/Id/AssignedGenerator.php
+++ b/lib/Doctrine/ORM/Id/AssignedGenerator.php
@@ -55,12 +55,8 @@ class AssignedGenerator extends AbstractIdGenerator
             }
 
             if (isset($class->associationMappings[$idField])) {
-                if ( ! $em->getUnitOfWork()->isInIdentityMap($value)) {
-                    throw ORMException::entityMissingForeignAssignedId($entity, $value);
-                }
-
                 // NOTE: Single Columns as associated identifiers only allowed - this constraint it is enforced.
-                $value = current($em->getUnitOfWork()->getEntityIdentifier($value));
+                $value = $em->getUnitOfWork()->getSingleIdentifierValue($value);
             }
 
             $identifier[$idField] = $value;
diff --git a/lib/Doctrine/ORM/Utility/IdentifierFlattener.php b/lib/Doctrine/ORM/Utility/IdentifierFlattener.php
index bb84c6151..d16da3255 100644
--- a/lib/Doctrine/ORM/Utility/IdentifierFlattener.php
+++ b/lib/Doctrine/ORM/Utility/IdentifierFlattener.php
@@ -76,7 +76,9 @@ final class IdentifierFlattener
                     $class->associationMappings[$idField]['targetEntity']
                 );
 
-                $associatedId = $this->unitOfWork->getEntityIdentifier($idValue);
+                $associatedId = $this->unitOfWork->isInIdentityMap($idValue)
+                    ? $this->unitOfWork->getEntityIdentifier($idValue)
+                    : $targetClassMetadata->getIdentifierValues($idValue);
 
                 $flatId[$idField] = $associatedId[$targetClassMetadata->identifier[0]];
             } else {