diff --git a/Documentation/Manual.rst b/Documentation/Manual.rst
index a95ee28adc8aa9bc0b4dcb6d6ab54cbcf1ff1879..c4f9e39ebfa7295e388aaa056d929bc765b25973 100644
--- a/Documentation/Manual.rst
+++ b/Documentation/Manual.rst
@@ -127,6 +127,14 @@ If there are problems with converting/downloading FE_GROUP protected pages, chec
     and so on! Typically some of them fails to load and wkhtml stops running! Verify the correct loading of all elements
     by calling the site via a regular browser and bypassing any browser cache (Ctrl F5).
 
+.. note::
+
+   On Ubuntu, Apache is started by default with `LANG=C`. This is true even when the OS default locale is set to `en_US.UTF-8`.
+   Furthermore, all child processes of Apache will inherit `LANG=C`. Some PHP functions (like 'escapeshellarg()')
+   or `wkhtml` will strip all non-ASCII characters (e.g. commandline arguments).
+
+   Let Apache run with the system locale: `/etc/apache/envvars`, activate the line `. /etc/default/locale` and restart Apache.
+
 Checklist wkhtml problems
 """""""""""""""""""""""""