diff -u b/core/includes/install.core.inc b/core/includes/install.core.inc
--- b/core/includes/install.core.inc
+++ b/core/includes/install.core.inc
@@ -1307,7 +1307,6 @@
  */
 function install_select_language_form($form, &$form_state, $files) {
   include_once DRUPAL_ROOT . '/core/includes/standard.inc';
-  include_once DRUPAL_ROOT . '/core/modules/language/language.module';
   include_once DRUPAL_ROOT . '/core/modules/language/language.negotiation.inc';
 
   $standard_languages = standard_language_list();
@@ -1369,6 +1368,7 @@
  */
 function install_select_language_form($form, &$form_state, $files) {
   include_once DRUPAL_ROOT . '/core/includes/standard.inc';
+  include_once DRUPAL_ROOT . '/core/modules/language/language.module';
   include_once DRUPAL_ROOT . '/core/modules/language/language.negotiation.inc';
 
   $standard_languages = standard_language_list();
diff -u b/core/modules/language/language.admin.inc b/core/modules/language/language.admin.inc
--- b/core/modules/language/language.admin.inc
+++ b/core/modules/language/language.admin.inc
@@ -821,7 +821,6 @@
   $form = array();
 
   // Initialize a language list to the ones available, including English.
-  drupal_static_reset('language_list');
   $languages = language_list();
 
   $existing_languages = array();
@@ -845,7 +844,6 @@
   }
 
   $form['mappings'] = array(
-    '#type' => 'container',
     '#tree' => TRUE,
     '#theme' => 'language_negotiation_configure_browser_form_table',
   );
@@ -890,8 +888,6 @@
     '#default_value' => '',
   );
 
-  $form_state['redirect'] = 'admin/config/regional/language/detection';
-
   $form['actions']['#type'] = 'actions';
   $form['actions']['submit'] = array(
     '#type' => 'submit',
@@ -954,10 +950,10 @@
     foreach ($mappings as $key => $data) {
       // Make sure browser_langcode is unique.
       if (array_key_exists($data['browser_langcode'], $unique_values)) {
-        form_set_error('mappings][' . $key . '][browser_langcode', 'Browser language codes must be unique.');
+        form_set_error('mappings][' . $key . '][browser_langcode', t('Browser language codes must be unique.'));
       }
       elseif (preg_match('/[^a-z\-]/', $data['browser_langcode'])) {
-        form_set_error('mappings][' . $key . '][browser_langcode', 'Browser language codes can only contain lowercase letters and a hyphen(-).');
+        form_set_error('mappings][' . $key . '][browser_langcode', t('Browser language codes can only contain lowercase letters and a hyphen(-).'));
       }
       $unique_values[$data['browser_langcode']] = $data['drupal_langcode'];
     }
@@ -968,10 +964,10 @@
   if (!empty($data['browser_langcode'])) {
     // Make sure browser_langcode is unique.
     if (array_key_exists($data['browser_langcode'], $unique_values)) {
-      form_set_error('mappings][' . $key . '][browser_langcode', 'Browser language codes must be unique.');
+      form_set_error('mappings][' . $key . '][browser_langcode', t('Browser language codes must be unique.'));
     }
     elseif (preg_match('/[^a-z\-]/', $data['browser_langcode'])) {
-      form_set_error('mappings][' . $key . '][browser_langcode', 'Browser language codes can only contain lowercase letters and a hyphen(-).');
+      form_set_error('mappings][' . $key . '][browser_langcode', t('Browser language codes can only contain lowercase letters and a hyphen(-).'));
     }
     $unique_values[$data['browser_langcode']] = $data['drupal_langcode'];
   }
@@ -987,6 +983,7 @@
   if (!empty($mappings)) {
     language_set_browser_drupal_langcode_mappings($mappings);
   }
+  $form_state['redirect'] = 'admin/config/regional/language/detection';
 }
 
 /**
diff -u b/core/modules/language/language.module b/core/modules/language/language.module
--- b/core/modules/language/language.module
+++ b/core/modules/language/language.module
@@ -616,8 +616,7 @@
 function language_get_browser_drupal_langcode_mappings() {
   $config = config('language.mappings');
   if ($config->isNew()) {
-    config_install_default_config('module', 'language');
-    $config = config('language.mappings');
+    return array();
   }
   return $config->get();
 }
diff -u b/core/modules/language/language.negotiation.inc b/core/modules/language/language.negotiation.inc
--- b/core/modules/language/language.negotiation.inc
+++ b/core/modules/language/language.negotiation.inc
@@ -126,7 +126,10 @@
   asort($browser_langcodes);
   foreach ($browser_langcodes as $langcode => $qvalue) {
     // For Chinese languages the generic tag is either zh-hans or zh-hant, so we
-    // need to handle this separately.
+    // need to handle this separately, we can not split $langcode on the
+    // first occurence of '-' otherwise we get a non-existing language zh.
+    // All other languages use a langcode without a '-', so we can safely split
+    // on the first occurence of it.
     $generic_tag = '';
     if (strlen($langcode) > 7 && (substr($langcode, 0, 7) == 'zh-hant' || substr($langcode, 0, 7) == 'zh-hans')) {
       $generic_tag = substr($langcode, 0, 7);
diff -u b/core/modules/language/lib/Drupal/language/Tests/LanguageBrowserDetectionUnitTest.php b/core/modules/language/lib/Drupal/language/Tests/LanguageBrowserDetectionUnitTest.php
--- b/core/modules/language/lib/Drupal/language/Tests/LanguageBrowserDetectionUnitTest.php
+++ b/core/modules/language/lib/Drupal/language/Tests/LanguageBrowserDetectionUnitTest.php
@@ -184,7 +184,7 @@
     $message = t('Are you sure you want to delete @browser_langcode?', array(
       '@browser_langcode' => $browser_langcode,
     ));
-    $this->assertRaw($message, 'Question found.');
+    $this->assertRaw($message);
 
     // Confirm the delete.
     $edit = array();
@@ -199,12 +199,13 @@
       'new_mapping[drupal_langcode]' => 'en',
     );
     $this->drupalPost('admin/config/regional/language/detection/browser', $edit, t('Save configuration'));
+    $this->drupalGet('admin/config/regional/language/detection/browser');
     $this->assertField('edit-mappings-xx-browser-langcode', 'xx', 'Browser language code found.');
     $this->assertField('edit-mappings-xx-drupal-langcode', 'en', 'Drupal language code found.');
 
     // Add the same custom mapping again.
     $this->drupalPost('admin/config/regional/language/detection/browser', $edit, t('Save configuration'));
-    $this->assertText('Browser language codes must be unique.', 'Error message displayed.');
+    $this->assertText('Browser language codes must be unique.');
 
     // Change browser language code of our custom mapping to zh-sg.
     $edit = array(
@@ -212,7 +213,7 @@
       'mappings[xx][drupal_langcode]' => 'en',
     );
     $this->drupalPost('admin/config/regional/language/detection/browser', $edit, t('Save configuration'));
-    $this->assertText(t('Browser language codes must be unique.'), 'Error message displayed.');
+    $this->assertText(t('Browser language codes must be unique.'));
 
     // Change Drupal language code of our custom mapping to zh-hans.
     $edit = array(
@@ -220,6 +221,7 @@
       'mappings[xx][drupal_langcode]' => 'zh-hans',
     );
     $this->drupalPost('admin/config/regional/language/detection/browser', $edit, t('Save configuration'));
+    $this->drupalGet('admin/config/regional/language/detection/browser');
     $this->assertField('edit-mappings-xx-browser-langcode', 'xx', 'Browser language code found.');
     $this->assertField('edit-mappings-xx-drupal-langcode', 'zh-hans', 'Drupal language code found.');
   }