diff --git a/test/lisp/emacs-lisp/shortdoc-tests.el b/test/lisp/emacs-lisp/shortdoc-tests.el
index 914aee633ee..516d095767f 100644
--- a/test/lisp/emacs-lisp/shortdoc-tests.el
+++ b/test/lisp/emacs-lisp/shortdoc-tests.el
@@ -22,6 +22,7 @@
 (require 'ert)
 (require 'shortdoc)
 (require 'subr-x) ; `string-pad' in shortdoc group needed at run time
+(require 'regexp-opt)    ; `regexp-opt-charset' not autoloaded
 
 (defun shortdoc-tests--tree-contains (tree fun)
   "Whether TREE contains a call to FUN."