diff --git a/packages/types/src/serde.ts b/packages/types/src/serde.ts
index 1881d40fb4e4..03fb3ff29ac0 100644
--- a/packages/types/src/serde.ts
+++ b/packages/types/src/serde.ts
@@ -26,7 +26,7 @@ declare global {
   /**
    * @public
    */
-  export interface ReadableStream {}
+  export interface ReadableStream<R = any> {}
   /**
    * @public
    */