diff --git a/lisp/emacs-lisp/byte-opt.el b/lisp/emacs-lisp/byte-opt.el
index f75be3f71ad..e6f18590705 100644
--- a/lisp/emacs-lisp/byte-opt.el
+++ b/lisp/emacs-lisp/byte-opt.el
@@ -1599,6 +1599,12 @@ byte-optimize-append
                          (cdr args))
                    (cdr newargs)))
 
+            ;; (append '(C1...) ... '(C2...)) -> (append C1... ... C2...)
+            ((cl-loop for arg in args
+                      always (and (eq (car arg) 'quote)
+                                  (proper-list-p (cdr arg))))
+             `',(mapcan #'cadr args))
+
             ;; non-terminal arg
             ((cdr args)
              (cond