diff --git a/conf.py b/conf.py
index 67c77b7..4ca4da9 100644
--- a/conf.py
+++ b/conf.py
@@ -21,8 +21,8 @@
 copyright = '2019--2024, EditorConfig Team'
 author = 'EditorConfig Team'
 
-version = '0.16.0'
-release = '0.16.0'
+version = '0.16.1'
+release = '0.16.1'
 
 # -- General configuration ---------------------------------------------------
 
diff --git a/index.rst b/index.rst
index 74f1120..9abf5fa 100644
--- a/index.rst
+++ b/index.rst
@@ -229,7 +229,9 @@ and the supported values associated with them:
        Only one language can be specified.  There is no default value.
 
        The format is ``ss`` or ``ss-TT``, where ``ss`` is an `ISO 639`_
-       language code and ``TT`` is an `ISO 3166`_ territory identifier.
+       two-letter language code and ``TT`` is an `ISO 3166`_ two-letter
+       territory identifier.  (Therefore ``spelling_language`` must be
+       either two or five characters long.)
 
        **Note:** This property does **not** specify the charset to be used.
        The charset is in separate property ``charset``.