diff --git a/lisp/emacs-lisp/cl-macs.el b/lisp/emacs-lisp/cl-macs.el
index 06a09885c88..44ebadeebff 100644
--- a/lisp/emacs-lisp/cl-macs.el
+++ b/lisp/emacs-lisp/cl-macs.el
@@ -3460,6 +3460,7 @@ Of course, we really can't know that for sure, so it's just a heuristic."
            (or (cdr (assq sym byte-compile-function-environment))
                (cdr (assq sym macroexpand-all-environment))))))
 
+;; Please keep it in sync with `comp-known-predicates'.
 (pcase-dolist (`(,type . ,pred)
                ;; Mostly kept in alphabetical order.
                '((array		. arrayp)
diff --git a/lisp/emacs-lisp/comp.el b/lisp/emacs-lisp/comp.el
index a833bf5bfc4..46d2896f2be 100644
--- a/lisp/emacs-lisp/comp.el
+++ b/lisp/emacs-lisp/comp.el
@@ -188,6 +188,9 @@ Useful to hook into pass checkers.")
    finally return h)
   "Hash table function -> `comp-constraint'.")
 
+;; Keep it in sync with the `cl-deftype-satisfies' property set in
+;; cl-macs.el. We can't use `cl-deftype-satisfies' directly as the
+;; relation type <-> predicate is not bijective (bug#45576).
 (defconst comp-known-predicates
   '((arrayp              . array)
     (atom		 . atom)