diff --git a/core/modules/language/language.module b/core/modules/language/language.module
index 3486ff4..d64d224 100644
--- a/core/modules/language/language.module
+++ b/core/modules/language/language.module
@@ -30,7 +30,7 @@ function language_help($path, $arg) {
       return '<p>' . t('Add a language to be supported by your site. If your desired language is not available, pick <em>Custom language...</em> at the end and provide a language code and other details manually.') . '</p>';
 
     case 'admin/config/regional/language/detection':
-      $output = '<p>' . t("Define how to decide which language is used to display page elements (primarily text provided by Drupal and modules, such as field labels and help text). This decision is made by evaluating a series of detection methods for languages; the first detection method that gets a result will determine which language is used for that type of text. Define the order of evaluation of language detection methods on this page.") . '</p>';
+      $output = '<p>' . t("Define how to decide which language is used to display page elements (primarily text provided by Drupal and modules, such as field labels and help text). This decision is made by evaluating a series of detection methods for languages; the first detection method that gets a result will determine which language is used for that type of text. Be aware that some language negotiation methods are unreliable under certain conditions, such as browser detection when page-caching is enabled and a user is not currently logged in. Define the order of evaluation of language detection methods on this page.") . '</p>';
       return $output;
 
     case 'admin/config/regional/language/detection/session':