#17714: document that the base64 codec adds a trailing newline.
diff --git a/Doc/library/codecs.rst b/Doc/library/codecs.rst
index 9e1a9c7..87c2b39 100644
--- a/Doc/library/codecs.rst
+++ b/Doc/library/codecs.rst
@@ -1194,7 +1194,9 @@
 | Codec              | Aliases                   | Purpose                   |
 +====================+===========================+===========================+
 | base64_codec       | base64, base-64           | Convert operand to MIME   |
-|                    |                           | base64                    |
+|                    |                           | base64 (the result always |
+|                    |                           | includes a trailing       |
+|                    |                           | ``'\n'``)                 |
 +--------------------+---------------------------+---------------------------+
 | bz2_codec          | bz2                       | Compress the operand      |
 |                    |                           | using bz2                 |