diff -u b/core/modules/system/templates/page.html.twig b/core/modules/system/templates/page.html.twig
--- b/core/modules/system/templates/page.html.twig
+++ b/core/modules/system/templates/page.html.twig
@@ -88,11 +88,11 @@
       </div>{# ./name-and-slogan #}
     {% endif %}
 
-    {{ page.header_second }}
+    {{ page.header_first }}
   </header>
 
+  {{ page.header_second }}
   {{ page.header_third }}
-  {{ page.header_first }}
 
   {{ page.breadcrumb }}
 
diff -u b/core/themes/classy/templates/layout/page.html.twig b/core/themes/classy/templates/layout/page.html.twig
--- b/core/themes/classy/templates/layout/page.html.twig
+++ b/core/themes/classy/templates/layout/page.html.twig
@@ -86,11 +86,11 @@
       </div>{# ./name-and-slogan #}
     {% endif %}
 
-    {{ page.header_second }}
+    {{ page.header_first }}
   </header>
 
+  {{ page.header_second }}
   {{ page.header_third }}
-  {{ page.header_first }}
 
   {{ page.breadcrumb }}
 
only in patch2:
unchanged:
--- a/core/modules/system/system.install
+++ b/core/modules/system/system.install
@@ -1085,3 +1085,34 @@ function system_schema() {
 
   return $schema;
 }
+
+/**
+ * @addtogroup updates-8.0.0-beta
+ * @{
+ */
+
+/**
+ * Move blocks inside header regions to the renamed header regions.
+ */
+function system_update_8001() {
+  /* @var \Drupal\block\BlockInterface[] $blocks */
+  $blocks = entity_load_multiple_by_properties('block', ['region' => 'header']);
+  foreach ($blocks as $block) {
+    $block->setRegion('header_first');
+    $block->save();
+  }
+  $blocks = entity_load_multiple_by_properties('block', ['region' => 'secondary_menu']);
+  foreach ($blocks as $block) {
+    $block->setRegion('header_second');
+    $block->save();
+  }
+  $blocks = entity_load_multiple_by_properties('block', ['region' => 'primary_menu']);
+  foreach ($blocks as $block) {
+    $block->setRegion('header_third');
+    $block->save();
+  }
+}
+
+/**
+ * @} End of "addtogroup updates-8.0.0-beta".
+ */