diff --git a/core/lib/Drupal/Core/Render/MainContent/HtmlRenderer.php b/core/lib/Drupal/Core/Render/MainContent/HtmlRenderer.php
index cd0d482..de4d6bc 100644
--- a/core/lib/Drupal/Core/Render/MainContent/HtmlRenderer.php
+++ b/core/lib/Drupal/Core/Render/MainContent/HtmlRenderer.php
@@ -195,7 +195,8 @@ protected function prepare(array $main_content, Request $request, RouteMatchInte
     // Determine the title: use the title provided by the main content if any,
     // otherwise get it from the routing information.
     $get_title = function (array $main_content) use ($request, $route_match) {
-      return isset($main_content['#title']) ? $main_content['#title'] : $this->titleResolver->getTitle($request, $route_match->getRouteObject());
+      $this_title = isset($main_content['#title']) ? $main_content['#title'] : $this->titleResolver->getTitle($request, $route_match->getRouteObject());
+      return isset($this_title['#markup']) ? $this->renderer->render($this_title, FALSE) : $this_title;
     };
 
     // If the _controller result already is #type => page,
diff --git a/core/modules/block/src/Plugin/DisplayVariant/BlockPageVariant.php b/core/modules/block/src/Plugin/DisplayVariant/BlockPageVariant.php
index 5785f8d..e0b41c6 100644
--- a/core/modules/block/src/Plugin/DisplayVariant/BlockPageVariant.php
+++ b/core/modules/block/src/Plugin/DisplayVariant/BlockPageVariant.php
@@ -190,7 +190,7 @@ public function build() {
     // Analogously for the page title.
     if (!$title_block_displayed) {
       $build['title'] = [
-        '#markup' => $this->title,
+        '#markup' => ['#markup' => $this->title],
       ];
     }