Reword

Author: javiereguiluz

components/serializer.rst

@@ -169,11 +169,11 @@ needs three parameters:
     Support for the ``allow_extra_attributes`` key in the context was introduced
     in Symfony 3.3.
 
-By default, additional attributes that are not mapped to the denormalized
-object will be ignored by the Serializer component. Include a
-``ClassMetadataFactory`` when constructing the normalizer and set the
-``allow_extra_attributes`` key of the deserialization context to ``false`` to
-let the serializer throw an exception when additional attributes are passed::
+By default, additional attributes that are not mapped to the denormalized object
+will be ignored by the Serializer component. If you prefer to throw an exception
+when this happens, set the ``allow_extra_attributes`` context option to
+``false`` and provide an object that implements ``ClassMetadataFactoryInterface`
+when constructing the normalizer::
 
     $data = <<<EOF
     <person>