diff --git a/doc/contribute/modifying_contributions.rst b/doc/contribute/modifying_contributions.rst
index 0dd9a24b23c73..46afd6b4077f5 100644
--- a/doc/contribute/modifying_contributions.rst
+++ b/doc/contribute/modifying_contributions.rst
@@ -64,6 +64,13 @@ If the original patches are substantially modified, the developer can either:
   submitted work is based on (mentioning, for example, the original PR
   number).
 
+.. note::
+
+  In any case commits that include content from both the original and
+  modifying author **must** include the ``Signed-off-by`` statements
+  from the original commit that provided the content as well as one from
+  the modifying author.  See :ref:`DCO`.
+
 .. note::
   Contributors should uncheck the box *“Allow Edits By Maintainers"*
   to indicate that they do not wish their patches to be amended,