Search builder: alphanumeric checkbox not returning correct results

Have noticed an error in results when using search builder to search on a custom field of type alphanumeric checkbox. Using a simple example, have searched the following query:
Contact type = Individual AND Custom field set:custom field = value

Advanced search returns the correct results whereas search builder returns none or incorrect results.

Have tried this and replicated on Civi 4.2.8, 4.3.7 and 4.4.0 on both Wordpress and Drupal installations.
Can't seem to test this on demo sites:
demo site 4.4.1 throws generic DB error when trying to save a contact with one of the checkboxes ticked on a custom field
demo site 4.3.8 throws error 'not of the type int' when trying to save a contact with one of the checkboxes ticked on a custom field