diff --git a/lisp/emacs-lisp/package-vc.el b/lisp/emacs-lisp/package-vc.el
index 8f62e7d65f3..b28e33b3b89 100644
--- a/lisp/emacs-lisp/package-vc.el
+++ b/lisp/emacs-lisp/package-vc.el
@@ -747,11 +747,14 @@ package-vc-install
 symbol whose name is the package name, and the URL for the
 package will be taken from the package's metadata.
 
-By default, this function installs the last version of the package
-available from its repository, but if REV is given and non-nil, it
-specifies the revision to install.  If REV has the special value
-`:last-release' (interactively, the prefix argument), that stands
-for the last released version of the package.
+By default, this function installs the last revision of the
+package available from its repository, but if REV is given and
+non-nil, it specifies the revision to install.  If REV has the
+special value `:last-release' (interactively, the prefix
+argument), an attempt is made to find the revision of the latest
+release.  This is done by looking up the last revision that
+modified the \"Version\" header, as described in the Info
+node `(elisp) Library Headers'.
 
 Optional argument BACKEND specifies the VC backend to use for cloning
 the package's repository; this is only possible if NAME-OR-URL is a URL,