diff --git a/cslug/_version.py b/cslug/_version.py
index d4594c6..fe1531e 100644
--- a/cslug/_version.py
+++ b/cslug/_version.py
@@ -2,5 +2,5 @@
 """
 """
 
-__version__ = '0.3.0'
+__version__ = '0.4.0'
 __version_info__ = tuple(map(int, __version__.split(".")))
diff --git a/docs/source/conf.py b/docs/source/conf.py
index 1fa17a3..3e3e8d0 100644
--- a/docs/source/conf.py
+++ b/docs/source/conf.py
@@ -133,6 +133,11 @@
 Changelog
 =========
 
+.. role:: red
+    :class: in-red
+
+Release history for |cslug|.
+Breaking changes are :red:`highlighted in red` text.
 
 """ + "\n".join(f"v{i.stem}\n-{'-' * len(i.stem)}\n\n"
                 f".. rst-class:: spacious\n\n"
diff --git a/docs/source/static/theme-overrides.css b/docs/source/static/theme-overrides.css
index 8876981..6e9824f 100644
--- a/docs/source/static/theme-overrides.css
+++ b/docs/source/static/theme-overrides.css
@@ -82,3 +82,8 @@ div[class*="highlight-py"] .highlight, div[class*="highlight-default"] .highligh
 .wy-nav-content-wrap {
   margin-left: min(28%, 300px);
 }
+
+/* Custom `.. rst-class:: in-red` blocks. */
+.in-red {
+  color: darkred;
+}
diff --git a/history/0.4.0.rst b/history/0.4.0.rst
new file mode 100644
index 0000000..508369a
--- /dev/null
+++ b/history/0.4.0.rst
@@ -0,0 +1,19 @@
+*   Force ``setup.py bdist_wheel`` to run ``clean --all``.
+    Doing so blocks setuptools from dumping files for the wrong platform from
+    the build cache folder into a wheel without any check to see if it is
+    required.
+    See :class:`cslug.building.bdist_wheel` for details.
+
+* Support Android running Termux_.
+
+*   .. rst-class:: in-red
+
+        Drop the :c:`mblen()` function from :mod:`cslug.stdlib` due to its
+        unavailability on Android.
+
+*   Support Cygwin Python and Cygwin native |gcc|.
+    Formerly, |cslug| supported a Cygwin environment but only using a regular
+    MSVC build of Python and |gcc| cross compile headers for building generic
+    Windows applications.
+
+.. _Termux: https://termux.com/