diff --git a/doc/emacs/vc1-xtra.texi b/doc/emacs/vc1-xtra.texi
index 66d3f51c306..23d5f504322 100644
--- a/doc/emacs/vc1-xtra.texi
+++ b/doc/emacs/vc1-xtra.texi
@@ -291,8 +291,13 @@ When collaborating on projects it is common to send patches via email,
 to share changes.  If you wish to do this using VC, you can use the
 @code{vc-prepare-patch} command.  This will prompt you for the
 revisions you wish to share, and which destination email address(es)
-to use.  The command will then prepare those revisions using your
-@abbr{MUA, Mail User Agent} for you to review and send.
+to use.  The revisions are separated using commas (or whatever was
+configured by @var{crm-separator}).  The command will then prepare
+those revisions using your @abbr{MUA, Mail User Agent} for you to
+review and send.
+
+When invoked interactively in a Log View buffer with marked revisions,
+these revisions will be used.
 
 @vindex vc-prepare-patches-separately
 Depending on the value of the user option