diff --git a/lisp/emacs-lisp/ert-font-lock.el b/lisp/emacs-lisp/ert-font-lock.el
index c6fd65e1507..58c6c0311cd 100644
--- a/lisp/emacs-lisp/ert-font-lock.el
+++ b/lisp/emacs-lisp/ert-font-lock.el
@@ -36,6 +36,7 @@
 ;;; Code:
 
 (require 'ert)
+(require 'ert-x)
 (require 'newcomment)
 (require 'pcase)