diff --git a/django/db/models/fields/files.py b/django/db/models/fields/files.py
index 3d1291a..edc5566 100644
--- a/django/db/models/fields/files.py
+++ b/django/db/models/fields/files.py
@@ -180,14 +180,14 @@ class FileDescriptor(DeferredAttribute):
         # in __set__.
         file = super().__get__(instance, cls)
 
-        # If this value is a string (instance.file = "path/to/file") or None
+        # If this value is a string (instance.file = "path/to/file")
         # then we simply wrap it with the appropriate attribute class according
         # to the file field. [This is FieldFile for FileFields and
         # ImageFieldFile for ImageFields; it's also conceivable that user
         # subclasses might also want to subclass the attribute class]. This
         # object understands how to convert a path to a file, and also how to
         # handle None.
-        if isinstance(file, str) or file is None:
+        if isinstance(file, str):
             attr = self.field.attr_class(instance, self.field, file)
             instance.__dict__[self.field.attname] = attr