diff --git a/docs/handbook/image-file-formats.rst b/docs/handbook/image-file-formats.rst
index 04966d5df..b70503740 100644
--- a/docs/handbook/image-file-formats.rst
+++ b/docs/handbook/image-file-formats.rst
@@ -381,11 +381,12 @@ The :py:meth:`~PIL.Image.Image.save` method supports the following options:
 
     * ``keep``: Only valid for JPEG files, will retain the original image setting.
     * ``4:4:4``, ``4:2:2``, ``4:2:0``: Specific sampling values
-    * ``-1``: equivalent to ``keep``
     * ``0``: equivalent to ``4:4:4``
     * ``1``: equivalent to ``4:2:2``
     * ``2``: equivalent to ``4:2:0``
 
+    If absent, the setting will be determined by libjpeg or libjpeg-turbo.
+
 **qtables**
     If present, sets the qtables for the encoder. This is listed as an
     advanced option for wizards in the JPEG documentation. Use with