searches do not delimit custom field id properly - leading to incorrect results

reproduced on Demo by:

• create custom group (custom_group)
• add field (custom_field) to custom_group (text: multiselect – 11 options will be enough (I numbered mine 1-11)
• create user with custom_group -> custom_field set to 1
• create user with custom_group -> custom_field set to 11
• cunduct search for custom_field = 1
  Issue is that the search picks up ANY contacts with a '1' in the id, so includes both 1 & 11.

The search query used in the search does not seem to delimit the id of the option properly. The query I picked up using debugging log was:

ELECT contact_a.id as contact_id, contact_a.contact_type  as `contact_type`, contact_a.contact_sub_type  as `contact_sub_type`, contact_a.sort_name  as `sort_name`, civicrm_value_yp_programme_preference_13.id as civicrm_value_yp_programme_preference_13_id, civicrm_value_yp_programme_preference_13.ambitions_drop_down_215 as custom_215  FROM civicrm_prevnext_cache pnc INNER JOIN civicrm_contact contact_a ON contact_a.id = pnc.entity_id1 AND pnc.cacheKey = 'civicrm search a20200580d861f11dd91f607ce0eb1e0_2851'  
	LEFT JOIN civicrm_value_yp_programme_preference_13 ON civicrm_value_yp_programme_preference_13.entity_id = `contact_a`.id  WHERE  (  ( civicrm_value_yp_programme_preference_13.ambitions_drop_down_215 RLIKE '[[:cntrl:]]*8[[:cntrl:]]*' )  )  AND (contact_a.is_deleted = 0)  GROUP BY contact_a.id  ORDER BY pnc.id

This seems to be using:
[code:mysql]
WHERE ( ( civicrm_value_yp_programme_preference_13.ambitions_drop_down_215 RLIKE '[[:cntrl:]]8[[:cntrl:]]' )
[code]
whereas I need to CONCAT a CHAR(0) (or paste one) on each end of the id to delimit it and not get results from all id's containing a 1.