iThemes Security Breaks Password Rest

I have a wordpress multisite installation at Dreamhost. Everything is up-to-date. When iThemes Security is active, and a user attempts a password reset, the reset succeeds, but the user gets the message:

Warning: call_user_func_array() expects parameter 1 to be a valid callback, function ‘enforce_strong_password’ not found or invalid function name in …../wordpress/wp-includes/plugin.php on line 429

Warning: Cannot modify header information – headers already sent by (output started at …../wordpress/wp-includes/plugin.php:429) in /home/twegner/wedgeblade.net/wordpress/wp-includes/pluggable.php on line 896

When iThemes security is deactivated or deleted, the problem goes away. I guess iThemes security changes persist, so I could leave it deactivated, but it doesn’t seem like a good idea to use a broken plugin.

Suggestions (or alternatives) appreciated. Thanks.

https://ww.wp.xz.cn/plugins/better-wp-security/