diff --git a/packages/backend/src/env.ts b/packages/backend/src/env.ts
index 7815f48c..0673c2a2 100644
--- a/packages/backend/src/env.ts
+++ b/packages/backend/src/env.ts
@@ -33,6 +33,8 @@ export const env = createEnv({
 
         LOGTAIL_TOKEN: z.string().optional(),
         LOGTAIL_HOST: z.string().url().optional(),
+
+        INDEX_CONCURRENCY_MULTIPLE: z.number().optional(),
     },
     runtimeEnv: process.env,
     emptyStringAsUndefined: true,