diff --git a/app/helpers/languages_helper.rb b/app/helpers/languages_helper.rb
index 4427fee8d1..2a7677033c 100644
--- a/app/helpers/languages_helper.rb
+++ b/app/helpers/languages_helper.rb
@@ -221,23 +221,23 @@ module LanguagesHelper
   # but for presenting posting and filtering languages, we drop the country code and
   # fall back to the language code, thus skipping these locales there.
   UI_ONLY_REGIONAL_LOCALES = {
-    'en-GB': 'English (British)',
-    'es-AR': 'Español (Argentina)',
-    'es-MX': 'Español (México)',
-    'fr-CA': 'Français (Canadien)',
-    'pt-BR': 'Português (Brasil)',
-    'pt-PT': 'Português (Portugal)',
-    'sr-Latn': 'Srpski (latinica)',
+    'en-GB': ['English (British)', 'English (British)'].freeze,
+    'es-AR': ['Spanish (Argentina)', 'Español (Argentina)'].freeze,
+    'es-MX': ['Spanish (Mexico)', 'Español (México)'].freeze,
+    'fr-CA': ['French (Canadian)', 'Français (Canadien)'].freeze,
+    'pt-BR': ['Portuguese (Brasil)', 'Português (Brasil)'].freeze,
+    'pt-PT': ['Portuguese (Portugal)', 'Português (Portugal)'].freeze,
+    'sr-Latn': ['Serbian (Latin)', 'Srpski (latinica)'].freeze,
   }.freeze
 
+  KNOWN_LOCALES = {}.merge(SUPPORTED_LOCALES).merge(UI_ONLY_REGIONAL_LOCALES).freeze
+
   # Helper for self.sorted_locale_keys
   private_class_method def self.locale_name_for_sorting(locale)
     if locale.blank? || locale == 'und'
       '000'
-    elsif (supported_locale = SUPPORTED_LOCALES[locale.to_sym])
-      ASCIIFolding.new.fold(supported_locale[1]).downcase
-    elsif (regional_locale = UI_ONLY_REGIONAL_LOCALES[locale.to_sym])
-      ASCIIFolding.new.fold(regional_locale).downcase
+    elsif (known_locale = KNOWN_LOCALES[locale.to_sym])
+      ASCIIFolding.new.fold(known_locale[1]).downcase
     else
       locale
     end
@@ -251,10 +251,8 @@ module LanguagesHelper
   def native_locale_name(locale)
     if locale.blank? || locale == 'und'
       I18n.t('generic.none')
-    elsif (supported_locale = SUPPORTED_LOCALES[locale.to_sym])
-      supported_locale[1]
-    elsif (regional_locale = UI_ONLY_REGIONAL_LOCALES[locale.to_sym])
-      regional_locale
+    elsif (known_locale = KNOWN_LOCALES[locale.to_sym])
+      known_locale[1]
     else
       locale
     end
@@ -263,8 +261,8 @@ module LanguagesHelper
   def standard_locale_name(locale)
     if locale.blank?
       I18n.t('generic.none')
-    elsif (supported_locale = SUPPORTED_LOCALES[locale.to_sym])
-      supported_locale[0]
+    elsif (known_locale = KNOWN_LOCALES[locale.to_sym])
+      known_locale[0]
     else
       locale
     end
diff --git a/app/lib/activitypub/case_transform.rb b/app/lib/activitypub/case_transform.rb
index 93b4b98887..9977647ce0 100644
--- a/app/lib/activitypub/case_transform.rb
+++ b/app/lib/activitypub/case_transform.rb
@@ -14,8 +14,7 @@ module ActivityPub::CaseTransform
       when String
         camel_lower_cache[value] ||= if value.start_with?('_:')
                                        "_:#{value.delete_prefix('_:').underscore.camelize(:lower)}"
-                                     elsif LanguagesHelper::SUPPORTED_LOCALES.key?(value.to_sym) ||
-                                           LanguagesHelper::UI_ONLY_REGIONAL_LOCALES.key?(value.to_sym)
+                                     elsif LanguagesHelper::KNOWN_LOCALES.key?(value.to_sym)
                                        value
                                      else
                                        value.underscore.camelize(:lower)
diff --git a/lib/tasks/repo.rake b/lib/tasks/repo.rake
index e5dfb570d4..f14049ea0e 100644
--- a/lib/tasks/repo.rake
+++ b/lib/tasks/repo.rake
@@ -96,7 +96,7 @@ namespace :repo do
     end.uniq.compact
 
     missing_available_locales = locales_in_files - I18n.available_locales
-    supported_locale_codes    = Set.new(LanguagesHelper::SUPPORTED_LOCALES.keys + LanguagesHelper::UI_ONLY_REGIONAL_LOCALES.keys)
+    supported_locale_codes    = Set.new(LanguagesHelper::KNOWN_LOCALES.keys)
     missing_locale_names      = I18n.available_locales.reject { |locale| supported_locale_codes.include?(locale) }
 
     critical = false
diff --git a/spec/helpers/languages_helper_spec.rb b/spec/helpers/languages_helper_spec.rb
index eae54b61a4..4f1311f819 100644
--- a/spec/helpers/languages_helper_spec.rb
+++ b/spec/helpers/languages_helper_spec.rb
@@ -5,7 +5,7 @@ require 'rails_helper'
 describe LanguagesHelper do
   describe 'the SUPPORTED_LOCALES constant' do
     it 'includes all i18n locales' do
-      expect(Set.new(described_class::SUPPORTED_LOCALES.keys + described_class::UI_ONLY_REGIONAL_LOCALES.keys)).to include(*I18n.available_locales)
+      expect(Set.new(described_class::KNOWN_LOCALES.keys)).to include(*I18n.available_locales)
     end
   end