diff --git a/core/modules/language/language.negotiation.inc b/core/modules/language/language.negotiation.inc
index 8ae625d..63ffaa0 100644
--- a/core/modules/language/language.negotiation.inc
+++ b/core/modules/language/language.negotiation.inc
@@ -84,11 +84,18 @@ function language_from_browser($languages) {
     foreach ($matches as $match) {
       // Handle Chinese so it maps right, some browsers are sending
       // wrong langcodes.
-      if (strtolower($match[1]) === 'zh-tw') {
-        $match[1] = 'zh-hant';
-      }
-      elseif (strtolower($match[1]) === 'zh-cn') {
-        $match[1] = 'zh-hans';
+      switch (strtolower($match[1])) {
+        case 'zh-tw': // Taiwan.
+        case 'zh-hk': // Hong Kong.
+        case 'zh-mo': // Macau.
+        case 'zh-cht': // Traditional Chinese.
+          $match[1] = 'zh-hant';
+          break;
+        case 'zh-cn': // China.
+        case 'zh-sg': // Singapore.
+        case 'zh-chs': // Simplified Chinese.
+          $match[1] = 'zh-hans';
+          break;
       }
 
       // We can safely use strtolower() here, tags are ASCII.
diff --git a/core/modules/language/lib/Drupal/language/Tests/LanguageBrowserDetectionUnitTest.php b/core/modules/language/lib/Drupal/language/Tests/LanguageBrowserDetectionUnitTest.php
index 96e4653..beb18c5 100644
--- a/core/modules/language/lib/Drupal/language/Tests/LanguageBrowserDetectionUnitTest.php
+++ b/core/modules/language/lib/Drupal/language/Tests/LanguageBrowserDetectionUnitTest.php
@@ -134,9 +134,14 @@ class LanguageBrowserDetectionUnitTest extends UnitTestBase {
       'zh-hant, en-us;q=0.90, en;q=0.80, zh;q=0.70' => 'zh-hant',
       'zh-hans, en-us;q=0.90, en;q=0.80, zh;q=0.70' => 'zh-hans',
       'zh-cn' => 'zh-hans',
+      'zh-sg' => 'zh-hans',
       'zh-tw' => 'zh-hant',
-      'zh-hant' => 'zh-hant',
+      'zh-hk' => 'zh-hant',
+      'zh-mo' => 'zh-hant',
       'zh-hans' => 'zh-hans',
+      'zh-hant' => 'zh-hant',
+      'zh-chs' => 'zh-hans',
+      'zh-cht' => 'zh-hant',
     );
 
     foreach ($test_cases as $accept_language => $expected_result) {