diff --git a/app/models/locale_site_setting.rb b/app/models/locale_site_setting.rb
index 607a8e7cddd..fad31b53e1f 100644
--- a/app/models/locale_site_setting.rb
+++ b/app/models/locale_site_setting.rb
@@ -25,7 +25,17 @@ class LocaleSiteSetting < EnumSiteSetting
 
   def self.supported_locales
     @lock.synchronize do
-      @supported_locales ||= Dir.glob(File.join(Rails.root, 'config', 'locales', 'client.*.yml')).map { |x| x.split('.')[-2] }.sort
+      @supported_locales ||= begin
+        app_client_files = Dir.glob(
+          File.join(Rails.root, 'config', 'locales', 'client.*.yml')
+        )
+
+        plugin_client_files = Dir.glob(
+          File.join(Rails.root, 'plugins', '*', 'config', 'locales', 'client.*.yml')
+        )
+
+        (app_client_files + plugin_client_files).map { |x| x.split('.')[-2] }.uniq.sort
+      end
     end
   end
 
diff --git a/config/locales/names.yml b/config/locales/names.yml
index 60e9925014a..6f15ab632d6 100644
--- a/config/locales/names.yml
+++ b/config/locales/names.yml
@@ -119,6 +119,9 @@ eo:
 es:
   name: Spanish
   nativeName: Español
+es_MX:
+  name: Spanish
+  nativeName: Español (MX)
 et:
   name: Estonian
   nativeName: eesti
diff --git a/spec/models/locale_site_setting_spec.rb b/spec/models/locale_site_setting_spec.rb
index 115354701c1..ef81765dc07 100644
--- a/spec/models/locale_site_setting_spec.rb
+++ b/spec/models/locale_site_setting_spec.rb
@@ -14,7 +14,7 @@ describe LocaleSiteSetting do
 
   describe 'values' do
     it 'returns all the locales that we have translations for' do
-      expect(LocaleSiteSetting.values.map { |x| x[:value] }.sort).to eq(Dir.glob(File.join(Rails.root, 'config', 'locales', 'client.*.yml')).map { |x| x.split('.')[-2] }.sort)
+      expect(LocaleSiteSetting.values.map { |x| x[:value] }).to include(*Dir.glob(File.join(Rails.root, 'config', 'locales', 'client.*.yml')).map { |x| x.split('.')[-2] })
     end
   end