diff --git a/docs/ref/models/fields.txt b/docs/ref/models/fields.txt
index df3a07b499..1daf6e2940 100644
--- a/docs/ref/models/fields.txt
+++ b/docs/ref/models/fields.txt
@@ -239,7 +239,8 @@ you try to save a model with a duplicate value in a :attr:`~Field.unique`
 field, a :exc:`django.db.IntegrityError` will be raised by the model's
 :meth:`~django.db.models.Model.save` method.
 
-This option is valid on all field types except :class:`ManyToManyField`.
+This option is valid on all field types except :class:`ManyToManyField` and
+:class:`FileField`.
 
 ``unique_for_date``
 -------------------
@@ -437,7 +438,13 @@ A :class:`CharField` that checks that the value is a valid e-mail address.
 
 .. class:: FileField(upload_to=None, [max_length=100, **options])
 
-A file-upload field. Has one **required** argument:
+A file-upload field.
+
+.. note::
+    The ``primary_key`` and ``unique`` arguments are not supported, and will
+    raise a ``TypeError`` if used.
+
+Has one **required** argument:
 
 .. attribute:: FileField.upload_to