diff --git a/doc/markup/inline.rst b/doc/markup/inline.rst
index a59585bab..32360baf7 100644
--- a/doc/markup/inline.rst
+++ b/doc/markup/inline.rst
@@ -145,10 +145,15 @@ Cross-referencing arbitrary locations
      The same works for tables that are given an explicit caption using the
      :dudir:`table` directive.
 
-   * Labels that aren't placed before a section title can still be referenced
-     to, but you must give the link an explicit title, using this syntax:
+   * Labels that aren't placed before a section title can still be referenced,
+     but you must give the link an explicit title, using this syntax:
      ``:ref:`Link title <label-name>```.
 
+   .. note::
+
+      Reference labels must start with an underscore. When referencing a
+      label, the underscore must be omitted (see examples above).
+
    Using :rst:role:`ref` is advised over standard reStructuredText links to
    sections (like ```Section title`_``) because it works across files, when
    section headings are changed, and for all builders that support