diff --git a/core/src/main/resources/hudson/model/DirectoryBrowserSupport/plaindir.jelly b/core/src/main/resources/hudson/model/DirectoryBrowserSupport/plaindir.jelly
index 547bbe1acb50..2fbfd3d6ab9c 100644
--- a/core/src/main/resources/hudson/model/DirectoryBrowserSupport/plaindir.jelly
+++ b/core/src/main/resources/hudson/model/DirectoryBrowserSupport/plaindir.jelly
@@ -21,7 +21,7 @@ THE SOFTWARE.
 <?jelly escape-by-default='true'?>
 <j:jelly xmlns:j="jelly:core" xmlns:l="/lib/layout">
     <l:view contentType="text/html">
-        <html>
+        <html lang="${request2.locale.toLanguageTag()}">
             <body>
                 <j:choose>
                     <j:if test="${parentPath.size() ne 0}">
diff --git a/core/src/main/resources/lib/layout/layout.jelly b/core/src/main/resources/lib/layout/layout.jelly
index 25e7063723bb..35a539cfb1f9 100644
--- a/core/src/main/resources/lib/layout/layout.jelly
+++ b/core/src/main/resources/lib/layout/layout.jelly
@@ -101,7 +101,7 @@ THE SOFTWARE.
   </j:if>
 </j:if>
 <x:doctype name="html" />
-<html>
+<html lang="${request2.locale.toLanguageTag()}">
   <head data-rooturl="${rootURL}" data-resurl="${resURL}" data-imagesurl="${imagesURL}" resURL="${resURL}"
         data-extensions-available="${extensionsAvailable}"
         data-crumb-header="${h.getCrumbRequestField()}" data-crumb-value="${h.getCrumb(request2)}"
