diff --git a/core/modules/ckeditor/ckeditor.services.yml b/core/modules/ckeditor/ckeditor.services.yml
index ebd0021..7e7d471 100644
--- a/core/modules/ckeditor/ckeditor.services.yml
+++ b/core/modules/ckeditor/ckeditor.services.yml
@@ -2,7 +2,7 @@ services:
   plugin.manager.ckeditor.plugin:
     class: Drupal\ckeditor\CKEditorPluginManager
     arguments: ['@container.namespaces', '@cache.cache', '@language_manager', '@module_handler']
-  cache.ckeditor:
+  cache.ckeditor.languages:
     class: Drupal\Core\Cache\CacheBackendInterface
     tags:
       - { name: cache.bin }
diff --git a/core/modules/ckeditor/lib/Drupal/ckeditor/Plugin/Editor/CKEditor.php b/core/modules/ckeditor/lib/Drupal/ckeditor/Plugin/Editor/CKEditor.php
index d6b1767..94fa1ac 100644
--- a/core/modules/ckeditor/lib/Drupal/ckeditor/Plugin/Editor/CKEditor.php
+++ b/core/modules/ckeditor/lib/Drupal/ckeditor/Plugin/Editor/CKEditor.php
@@ -275,7 +275,7 @@ public function getLangcodes() {
     // be expensive to calculate all the time. The cache is cleared on core
     // upgrades which is the only situation the CKEditor file listing should
     // change.
-    $langcode_cache = cache('ckeditor')->get('langcodes');
+    $langcode_cache = cache('ckeditor.languages')->get('langcodes');
     if (!empty($langcode_cache)) {
       $langcodes = $langcode_cache->data;
     }
@@ -287,7 +287,7 @@ public function getLangcodes() {
         $langcode = basename($language_filename, '.js');
         $langcodes[$langcode] = $langcode;
       }
-      cache('ckeditor')->set('langcodes', $langcodes);
+      cache('ckeditor.languages')->set('langcodes', $langcodes);
     }
 
     // Get language mapping if available to map to Drupal language codes.
diff --git a/core/modules/language/language.negotiation.inc b/core/modules/language/language.negotiation.inc
index 8834812..dc69597 100644
--- a/core/modules/language/language.negotiation.inc
+++ b/core/modules/language/language.negotiation.inc
@@ -111,7 +111,13 @@ function language_from_browser($languages) {
       // so we multiply the qvalue by 1000 to avoid floating point comparisons.
       $langcode = strtolower($match[1]);
       $qvalue = isset($match[2]) ? (float) $match[2] : 1;
-      $browser_langcodes[$langcode] = (int) ($qvalue * 1000);
+      // Take the highest qvalue for this langcode. Although the request
+      // supposedly contains unique langcodes, our mapping possibly resolves
+      // to the same langcode for different qvalues. Keep the highest.
+      $browser_langcodes[$langcode] = max(
+        (int) ($qvalue * 1000),
+        (isset($browser_langcodes[$langcode]) ? $browser_langcodes[$langcode] : 0)
+      );
     }
   }