diff --git a/core/modules/block/js/block.admin.js b/core/modules/block/js/block.admin.js
index cc7b154..93d9229 100644
--- a/core/modules/block/js/block.admin.js
+++ b/core/modules/block/js/block.admin.js
@@ -43,17 +43,19 @@ function showBlockEntry (index, block) {
       if (query.length >= 2) {
         $blocks.each(showBlockEntry);
 
-        // Hide the category <details> if they don't have any visible rows.
         // Note that we first open all <details> to be able to use ':visible'.
+        // Mark the <details> elements that were closed before filtering, so
+        // they can be reclosed when filtering is removed.
+        $details.not('[open]').attr('data-drupal-block-state', 'forced-open');
+        // Hide the category <details> if they don't have any visible rows.
         $details.attr('open', 'open').each(hideCategoryDetails);
       }
       else {
         $blocks.show();
         $details.show();
-      }
-      // Once the query is completely gone, close all details elements.
-      if (query.length === 0) {
-        $details.removeAttr('open');
+        // Return <details> elements that had been closed before filtering
+        // to a closed state.
+        $details.filter('[data-drupal-block-state="forced-open"]').removeAttr('open data-drupal-block-state');
       }
     }