docs: update changelog and versionadded
diff --git a/docs/advanced/classes.rst b/docs/advanced/classes.rst
index e8940d8..f7db3ea 100644
--- a/docs/advanced/classes.rst
+++ b/docs/advanced/classes.rst
@@ -149,8 +149,7 @@
 will generally leave the C++ instance in an invalid state and cause undefined
 behavior if the C++ instance is subsequently used.
 
-.. versionadded:: 2.5.1
-
+.. versionchanged:: 2.6
    The default pybind11 metaclass will throw a ``TypeError`` when it detects
    that ``__init__`` was not called by a derived class.
 
@@ -597,6 +596,8 @@
 
     pybind11 does not support C++ destructors marked ``noexcept(false)``.
 
+.. versionadded:: 2.6
+
 .. _implicit_conversions:
 
 Implicit conversions
@@ -1147,6 +1148,8 @@
 
 .. note:: This attribute is currently ignored on PyPy
 
+.. versionadded:: 2.6
+
 Custom automatic downcasters
 ============================