diff --git a/src/rpc.ts b/src/rpc.ts
index 1fba228..b098eed 100644
--- a/src/rpc.ts
+++ b/src/rpc.ts
@@ -5,6 +5,7 @@ export const JsonRpcVersionSchema = z.literal("2.0");
 export const JsonRpcIdSchema = z.union([
   z.string().min(1),
   z.number().finite(),
+  z.null(),
 ]);
 
 export const JsonRpcIdempotencyMetadataSchema = z