diff --git a/core/modules/block/block.module b/core/modules/block/block.module
index 19a1301..5b30b4a 100644
--- a/core/modules/block/block.module
+++ b/core/modules/block/block.module
@@ -146,7 +146,10 @@ function block_rebuild() {
         // Disable blocks in invalid regions.
         if (!isset($regions[$block->getRegion()]) && $block->status()) {
           drupal_set_message(t('The block %info was assigned to the invalid region %region and has been disabled.', ['%info' => $block_id, '%region' => $block->getRegion()]), 'warning');
-          $block->disable()->save();
+          $block
+            ->setRegion(system_default_region($theme))
+            ->disable()
+            ->save();
         }
       }
     }
diff --git a/core/modules/block/tests/src/Kernel/BlockRebuildTest.php b/core/modules/block/tests/src/Kernel/BlockRebuildTest.php
index 13bacff..e2d555d 100644
--- a/core/modules/block/tests/src/Kernel/BlockRebuildTest.php
+++ b/core/modules/block/tests/src/Kernel/BlockRebuildTest.php
@@ -3,6 +3,7 @@
 namespace Drupal\Tests\block\Kernel;
 
 use Drupal\block\BlockInterface;
+use Drupal\block\Entity\Block;
 use Drupal\Core\StringTranslation\TranslatableMarkup;
 use Drupal\KernelTests\KernelTestBase;
 use Drupal\simpletest\BlockCreationTrait;
@@ -67,11 +68,18 @@ public function testRebuildNoInvalidBlocks() {
   public function testRebuildInvalidBlocks() {
     $this->placeBlock('system_powered_by_block', ['region' => 'content', 'theme' => 'classy']);
     $block = $this->placeBlock('system_powered_by_block', ['region' => 'INVALID', 'theme' => 'classy']);
+    $this->assertSame('INVALID', $block->getRegion());
+    $this->assertTrue($block->status());
 
     block_rebuild();
+    // Reload block entity.
+    $block = Block::load($block->id());
+
     $messages = drupal_get_messages();
     $expected = ['warning' => [new TranslatableMarkup('The block %info was assigned to the invalid region %region and has been disabled.', ['%info' => $block->id(), '%region' => 'INVALID'])]];
     $this->assertEquals($expected, $messages);
+    $this->assertSame(system_default_region('classy'), $block->getRegion());
+    $this->assertFalse($block->status());
   }
 
 }