diff --git a/core/modules/block/block.install b/core/modules/block/block.install
index ea626a2..5e9cb60 100644
--- a/core/modules/block/block.install
+++ b/core/modules/block/block.install
@@ -63,7 +63,7 @@ function block_update_8001() {
             // fix their block placements manually OR alternatively contributed
             // modules can run their own update functions to update mappings
             // that they provide.
-            $backup_values[] = $context;
+            $backup_values[$context][] = $key;
             unset($visibility[$condition_plugin_id]);
             continue;
           }