diff --git a/core/modules/block/block.module b/core/modules/block/block.module
index fb5c2e0..c891659 100644
--- a/core/modules/block/block.module
+++ b/core/modules/block/block.module
@@ -127,13 +127,18 @@ function block_theme_initialize($theme) {
       // theme's default region.
       if (!isset($regions[$block->getRegion()])) {
         $default_block = system_get_info('theme', $theme)['block_default_region'];
-        if (isset($default_block) && isset($regions[$default_block])) {
-          $block->setRegion($default_block);
-        }
+        if (isset($default_block)) {
+          if (isset($regions[$default_block])) {
+            $block->setRegion($default_block);
+            }
+          else {
+            $block->setRegion(system_default_region($theme));
+            }
+          }
         else {
           $block->setRegion(system_default_region($theme));
+          }
         }
-      }
       $block->save();
     }
   }