Use of undefined constant

in admin/config/system/encrypt page on click of save configuration , i notice the below errors.how to fix the below issues in drupal 7 using encrypt module

Use of undefined constant REQUIREMENT_OK - assumed 'REQUIREMENT_OK' in encrypt_requirements() in line 90 in encrypt.install
Use of undefined constant REQUIREMENT_OK - assumed 'REQUIREMENT_OK' in encrypt_admin_settings() in line 43 in encrypt.admin.inc).
Use of undefined constant REQUIREMENT_ERROR - assumed 'REQUIREMENT_ERROR' in encrypt_admin_settings() in line 62 in encrypt.admin.inc).