diff --git a/migrations/000012_add_modules_series_path_index.down.sql b/migrations/000012_add_modules_series_path_index.down.sql
new file mode 100644
index 00000000..e5a46cb2
--- /dev/null
+++ b/migrations/000012_add_modules_series_path_index.down.sql
@@ -0,0 +1,9 @@
+-- Copyright 2020 The Go Authors. All rights reserved.
+-- Use of this source code is governed by a BSD-style
+-- license that can be found in the LICENSE file.
+
+BEGIN;
+
+DROP INDEX idx_modules_series_path;
+
+END;
diff --git a/migrations/000012_add_modules_series_path_index.up.sql b/migrations/000012_add_modules_series_path_index.up.sql
new file mode 100644
index 00000000..00b27554
--- /dev/null
+++ b/migrations/000012_add_modules_series_path_index.up.sql
@@ -0,0 +1,9 @@
+-- Copyright 2020 The Go Authors. All rights reserved.
+-- Use of this source code is governed by a BSD-style
+-- license that can be found in the LICENSE file.
+
+BEGIN;
+
+CREATE INDEX idx_modules_series_path ON modules(series_path);
+
+END;