diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index a83b7a5..44df583 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -2135,7 +2135,7 @@ function template_preprocess_html(&$variables) {
       '#tag' => 'meta',
       '#attributes' => array(
         'name' => 'viewport',
-        'content' => 'width=device-width',
+        'content' => 'width=device-width, initial-scale=1.0',
       ),
     ),
   );
diff --git a/core/modules/system/lib/Drupal/system/Tests/System/DefaultMobileMetaTagsTest.php b/core/modules/system/lib/Drupal/system/Tests/System/DefaultMobileMetaTagsTest.php
index ba0889f..16cbea7 100644
--- a/core/modules/system/lib/Drupal/system/Tests/System/DefaultMobileMetaTagsTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/System/DefaultMobileMetaTagsTest.php
@@ -24,7 +24,7 @@ function setUp() {
     $this->default_metatags = array(
       'MobileOptimized' => '<meta name="MobileOptimized" content="width" />',
       'HandheldFriendly' => '<meta name="HandheldFriendly" content="true" />',
-      'viewport' => '<meta name="viewport" content="width=device-width" />',
+      'viewport' => '<meta name="viewport" content="width=device-width, initial-scale=1.0" />',
     );
   }