diff --git a/doc/bookmarks.rst b/doc/bookmarks.rst
index bdab3a83a8..21d96e27c6 100644
--- a/doc/bookmarks.rst
+++ b/doc/bookmarks.rst
@@ -26,6 +26,7 @@ This is done by inserting into the query SQL comments between ``/*`` and
 ``*/``. Inside the comments, the special strings ``[VARIABLE{variable-number}]`` is used.
 Be aware that the whole query minus the SQL comments must be
 valid by itself, otherwise you won't be able to store it as a bookmark.
+Note also that the text 'VARIABLE' is case-sensitive.
 
 When you execute the bookmark, everything typed into the *Variables*
 input boxes on the query box page will replace the strings ``/*[VARIABLE{variable-number}]*/`` in