diff --git a/packages/hash-stream-node/src/readableStreamHasher.ts b/packages/hash-stream-node/src/readableStreamHasher.ts
index 420bb7787badf..29b41a07d401c 100644
--- a/packages/hash-stream-node/src/readableStreamHasher.ts
+++ b/packages/hash-stream-node/src/readableStreamHasher.ts
@@ -6,6 +6,7 @@ import { HashCalculator } from "./HashCalculator";
 import { isFileStream } from "./isFileStream";
 
 export const readableStreamHasher: StreamHasher<Readable> = (hashCtor: HashConstructor, readableStream: Readable) => {
+  // ToDo: throw if readableStream is already flowing and it's copy can't be created.
   // ToDo: create accurate copy if filestream is created from file descriptor.
   const streamToPipe = isFileStream(readableStream)
     ? createReadStream(readableStream.path, {