core/includes/common.inc        | 5 +++++
 core/modules/block/block.module | 6 +++---
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/core/includes/common.inc b/core/includes/common.inc
index e6536fb..3f78397 100644
--- a/core/includes/common.inc
+++ b/core/includes/common.inc
@@ -2507,6 +2507,11 @@ function drupal_prepare_page($page) {
     $page['page_bottom'] = $pseudo_page_bottom;
   }
 
+  // @todo Clean this up as part of https://www.drupal.org/node/2352155.
+  if (\Drupal::moduleHandler()->moduleExists('block')) {
+    _block_page_build($page);
+  }
+
   // If no module has taken care of the main content, add it to the page now.
   // This allows the site to still be usable even if no modules that
   // control page regions (for example, the Block module) are enabled.
diff --git a/core/modules/block/block.module b/core/modules/block/block.module
index cbf56ab..e615100 100644
--- a/core/modules/block/block.module
+++ b/core/modules/block/block.module
@@ -64,11 +64,11 @@ function block_theme() {
 }
 
 /**
- * Implements hook_page_build().
- *
  * Renders blocks into their regions.
+ *
+ * @todo Clean this up as part of https://www.drupal.org/node/2352155.
  */
-function block_page_build(&$page) {
+function _block_page_build(&$page) {
   $theme = \Drupal::theme()->getActiveTheme()->getName();
 
   // Fetch a list of regions for the current theme.