diff --git a/db/post_migrate/20250909093241_reprepare_tmp_idx_events_where_project_target_type_missing.rb b/db/post_migrate/20250909093241_reprepare_tmp_idx_events_where_project_target_type_missing.rb
new file mode 100644
index 0000000000000000000000000000000000000000..18e0e09a216c4b5b06d202632e20d10dd876a9f5
--- /dev/null
+++ b/db/post_migrate/20250909093241_reprepare_tmp_idx_events_where_project_target_type_missing.rb
@@ -0,0 +1,32 @@
+# frozen_string_literal: true
+
+class ReprepareTmpIdxEventsWhereProjectTargetTypeMissing < Gitlab::Database::Migration[2.3]
+  milestone '18.4'
+
+  INDEX_NAME = :tmp_idx_events_where_project_target_type_missing
+
+  PREV_PROJECT_ACTIONS = [1, 5, 8, 9, 11].freeze # Defined in `/app/models/event.rb`
+  NEW_PROJECT_ACTIONS = [1, 8, 9, 11].freeze # Defined in `/app/models/event.rb`
+
+  def up
+    unprepare_async_index_by_name :events, INDEX_NAME
+
+    # rubocop:disable Migration/PreventIndexCreation -- temporary index for https://gitlab.com/gitlab-org/gitlab/-/issues/565788
+    prepare_async_index(
+      :events, :id,
+      where: "target_type IS NULL AND action IN (#{NEW_PROJECT_ACTIONS.join(',')}) AND project_id IS NOT NULL",
+      name: INDEX_NAME
+    )
+    # rubocop:enable Migration/PreventIndexCreation
+  end
+
+  def down
+    unprepare_async_index_by_name :events, INDEX_NAME
+
+    prepare_async_index(
+      :events, :id,
+      where: "target_type IS NULL AND action IN (#{PREV_PROJECT_ACTIONS.join(',')}) AND project_id IS NOT NULL",
+      name: INDEX_NAME
+    )
+  end
+end
diff --git a/db/schema_migrations/20250909093241 b/db/schema_migrations/20250909093241
new file mode 100644
index 0000000000000000000000000000000000000000..dfa6e33d8c9b53e1c5a31492b4dc6212beddcebc
--- /dev/null
+++ b/db/schema_migrations/20250909093241
@@ -0,0 +1 @@
+c94aa95e126cdf962140c4367800fdf51852e4f645b0e5c4b4abb8705e0506f5
\ No newline at end of file