diff --git a/lisp/vc/vc.el b/lisp/vc/vc.el
index b02a05eb664..65d126a6614 100644
--- a/lisp/vc/vc.el
+++ b/lisp/vc/vc.el
@@ -630,11 +630,14 @@
 ;;
 ;; - ignore-completion-table (directory)
 ;;
-;;   Return the completion table for files ignored by the current
+;;   Return the list of patterns for files ignored by the current
 ;;   version control system, e.g., the entries in `.gitignore' and
 ;;   `.bzrignore'.  The default behavior is to read the contents of
 ;;   the file returned by the `find-ignore-file' function.
 ;;
+;;   NOTE: The return value should be a list of strings, not a general
+;;   completion table value, despite what the name implies.
+;;
 ;; - find-ignore-file (file)
 ;;
 ;;   Return the ignore file that controls FILE, e.g. `.gitignore' or