diff --git a/app/models/form/admin_settings.rb b/app/models/form/admin_settings.rb
index 5f23e683b99..a19a6308fac 100644
--- a/app/models/form/admin_settings.rb
+++ b/app/models/form/admin_settings.rb
@@ -82,15 +82,17 @@ class Form::AdminSettings
   }.freeze
 
   DESCRIPTION_LIMIT = 200
+  DOMAIN_BLOCK_AUDIENCES = %w(disabled users all).freeze
+  REGISTRATION_MODES = %w(open approved none).freeze
 
   attr_accessor(*KEYS)
 
-  validates :registrations_mode, inclusion: { in: %w(open approved none) }, if: -> { defined?(@registrations_mode) }
+  validates :registrations_mode, inclusion: { in: REGISTRATION_MODES }, if: -> { defined?(@registrations_mode) }
   validates :site_contact_email, :site_contact_username, presence: true, if: -> { defined?(@site_contact_username) || defined?(@site_contact_email) }
   validates :site_contact_username, existing_username: true, if: -> { defined?(@site_contact_username) }
   validates :bootstrap_timeline_accounts, existing_username: { multiple: true }, if: -> { defined?(@bootstrap_timeline_accounts) }
-  validates :show_domain_blocks, inclusion: { in: %w(disabled users all) }, if: -> { defined?(@show_domain_blocks) }
-  validates :show_domain_blocks_rationale, inclusion: { in: %w(disabled users all) }, if: -> { defined?(@show_domain_blocks_rationale) }
+  validates :show_domain_blocks, inclusion: { in: DOMAIN_BLOCK_AUDIENCES }, if: -> { defined?(@show_domain_blocks) }
+  validates :show_domain_blocks_rationale, inclusion: { in: DOMAIN_BLOCK_AUDIENCES }, if: -> { defined?(@show_domain_blocks_rationale) }
   validates :media_cache_retention_period, :content_cache_retention_period, :backups_retention_period, numericality: { only_integer: true }, allow_blank: true, if: -> { defined?(@media_cache_retention_period) || defined?(@content_cache_retention_period) || defined?(@backups_retention_period) }
   validates :min_age, numericality: { only_integer: true }, allow_blank: true, if: -> { defined?(@min_age) }
   validates :site_short_description, length: { maximum: DESCRIPTION_LIMIT }, if: -> { defined?(@site_short_description) }
diff --git a/app/views/admin/settings/about/show.html.haml b/app/views/admin/settings/about/show.html.haml
index 1eb47a0b54e..adc8f1ff04a 100644
--- a/app/views/admin/settings/about/show.html.haml
+++ b/app/views/admin/settings/about/show.html.haml
@@ -24,7 +24,7 @@
     .fields-row__column.fields-row__column-6.fields-group
       = f.input :show_domain_blocks,
                 collection_wrapper_tag: 'ul',
-                collection: %i(disabled users all),
+                collection: f.object.class::DOMAIN_BLOCK_AUDIENCES,
                 include_blank: false,
                 item_wrapper_tag: 'li',
                 label_method: ->(value) { t("admin.settings.domain_blocks.#{value}") },
@@ -32,7 +32,7 @@
     .fields-row__column.fields-row__column-6.fields-group
       = f.input :show_domain_blocks_rationale,
                 collection_wrapper_tag: 'ul',
-                collection: %i(disabled users all),
+                collection: f.object.class::DOMAIN_BLOCK_AUDIENCES,
                 include_blank: false,
                 item_wrapper_tag: 'li',
                 label_method: ->(value) { t("admin.settings.domain_blocks.#{value}") },
diff --git a/app/views/admin/settings/registrations/show.html.haml b/app/views/admin/settings/registrations/show.html.haml
index cb5a3eb6baf..7303eca662a 100644
--- a/app/views/admin/settings/registrations/show.html.haml
+++ b/app/views/admin/settings/registrations/show.html.haml
@@ -18,7 +18,7 @@
   .fields-row
     .fields-row__column.fields-row__column-6.fields-group
       = f.input :registrations_mode,
-                collection: %w(open approved none),
+                collection: f.object.class::REGISTRATION_MODES,
                 include_blank: false,
                 label_method: ->(mode) { I18n.t("admin.settings.registrations_mode.modes.#{mode}") },
                 warning_hint: I18n.t('admin.settings.registrations_mode.warning_hint'),