diff --git a/packages/eventstream-handler-node/src/EventStreamPayloadHandler.spec.ts b/packages/eventstream-handler-node/src/EventStreamPayloadHandler.spec.ts
index d2a774126c6a..a2b8f25d0edd 100644
--- a/packages/eventstream-handler-node/src/EventStreamPayloadHandler.spec.ts
+++ b/packages/eventstream-handler-node/src/EventStreamPayloadHandler.spec.ts
@@ -9,6 +9,15 @@ jest.mock("./EventSigningStream");
 jest.mock("@smithy/eventstream-codec");
 
 describe(EventStreamPayloadHandler.name, () => {
+  const collectData = (stream: Readable) => {
+    const chunks: any = [];
+    return new Promise((resolve, reject) => {
+      stream.on("data", (chunk) => chunks.push(chunk));
+      stream.on("error", reject);
+      stream.on("end", () => resolve(Buffer.concat(chunks).toString("utf8")));
+    });
+  };
+
   const mockMessageSigner: MessageSigner = {
     sign: jest.fn(),
     signMessage: jest.fn(),
@@ -49,7 +58,7 @@ describe(EventStreamPayloadHandler.name, () => {
       utf8Decoder: mockUtf8Decoder,
       utf8Encoder: mockUtf8encoder,
     });
-    const mockRequest = { body: new Readable() } as HttpRequest;
+    const mockRequest = { body: new PassThrough() } as HttpRequest;
 
     try {
       await handler.handle(mockNextHandler, {
@@ -126,6 +135,42 @@ describe(EventStreamPayloadHandler.name, () => {
     });
   });
 
+  it("should start piping regardless of whether the downstream resolves", async () => {
+    const authorization =
+      "AWS4-HMAC-SHA256 Credential=AKID/20200510/us-west-2/foo/aws4_request, SignedHeaders=host, Signature=1234567890";
+    const originalPayload = new PassThrough();
+    const mockRequest = {
+      body: originalPayload,
+      headers: { authorization },
+    } as any;
+    const handler = new EventStreamPayloadHandler({
+      messageSigner: () => Promise.resolve(mockMessageSigner),
+      utf8Decoder: mockUtf8Decoder,
+      utf8Encoder: mockUtf8encoder,
+    });
+
+    (mockNextHandler as any).mockImplementationOnce(async (args: FinalizeHandlerArguments<any>) => {
+      const handledRequest = args.request as HttpRequest;
+
+      originalPayload.end("Some Data");
+      const collected = await collectData(handledRequest.body);
+
+      // this means the stream is flowing without this downstream middleware
+      // having resolved yet.
+      expect(collected).toEqual("Some Data");
+
+      return Promise.resolve({ output: { handledRequest } });
+    });
+
+    const {
+      output: { handledRequest },
+    } = await handler.handle(mockNextHandler, {
+      request: mockRequest,
+      input: {},
+    });
+    expect(handledRequest.body).not.toBe(originalPayload);
+  });
+
   it("should start piping to request payload through event signer if downstream middleware returns", async () => {
     const authorization =
       "AWS4-HMAC-SHA256 Credential=AKID/20200510/us-west-2/foo/aws4_request, SignedHeaders=host, Signature=1234567890";
@@ -155,14 +200,6 @@ describe(EventStreamPayloadHandler.name, () => {
     expect(handledRequest.body).not.toBe(originalPayload);
     // Expect the data from the output payload from eventstream payload handler the same as from the
     // stream supplied to the handler.
-    const collectData = (stream: Readable) => {
-      const chunks: any = [];
-      return new Promise((resolve, reject) => {
-        stream.on("data", (chunk) => chunks.push(chunk));
-        stream.on("error", reject);
-        stream.on("end", () => resolve(Buffer.concat(chunks).toString("utf8")));
-      });
-    };
     originalPayload.end("Some Data");
     const collected = await collectData(handledRequest.body);
     expect(collected).toEqual("Some Data");
diff --git a/packages/eventstream-handler-node/src/EventStreamPayloadHandler.ts b/packages/eventstream-handler-node/src/EventStreamPayloadHandler.ts
index c750f9158fa6..e17d6c6aa538 100644
--- a/packages/eventstream-handler-node/src/EventStreamPayloadHandler.ts
+++ b/packages/eventstream-handler-node/src/EventStreamPayloadHandler.ts
@@ -64,20 +64,9 @@ export class EventStreamPayloadHandler implements IEventStreamPayloadHandler {
       objectMode: true,
     });
 
-    let result: FinalizeHandlerOutput<any>;
-    try {
-      result = await next(args);
-    } catch (e) {
-      // Close the payload stream otherwise the retry would hang
-      // because of the previous connection.
-      request.body.end();
-      throw e;
-    }
-
-    // If response is successful, start piping the payload stream
-    const match = (request.headers["authorization"] || "").match(/Signature=([\w]+)$/);
+    const match = request.headers?.authorization?.match(/Signature=([\w]+)$/);
     // Sign the eventstream based on the signature from initial request.
-    const priorSignature = (match || [])[1] || (query && (query["X-Amz-Signature"] as string)) || "";
+    const priorSignature = match?.[1] ?? (query?.["X-Amz-Signature"] as string) ?? "";
     const signingStream = new EventSigningStream({
       priorSignature,
       eventStreamCodec: this.eventStreamCodec,
@@ -91,6 +80,16 @@ export class EventStreamPayloadHandler implements IEventStreamPayloadHandler {
       }
     });
 
+    let result: FinalizeHandlerOutput<any>;
+    try {
+      result = await next(args);
+    } catch (e) {
+      // Close the payload stream otherwise the retry would hang
+      // because of the previous connection.
+      request.body.end();
+      throw e;
+    }
+
     return result;
   }
 }
diff --git a/packages/middleware-eventstream/src/middleware-eventstream.integ.spec.ts b/packages/middleware-eventstream/src/middleware-eventstream.integ.spec.ts
index 2216bdda63bc..b412e9e98c68 100644
--- a/packages/middleware-eventstream/src/middleware-eventstream.integ.spec.ts
+++ b/packages/middleware-eventstream/src/middleware-eventstream.integ.spec.ts
@@ -30,15 +30,7 @@ describe("middleware-eventstream", () => {
         botAliasId: "undefined",
         localeId: "undefined",
         sessionId: "undefined",
-        requestEventStream: {
-          [Symbol.asyncIterator]() {
-            return {
-              next() {
-                return this as any;
-              },
-            };
-          },
-        },
+        requestEventStream: (async function* () {})(),
       });
 
       expect.assertions(2);
@@ -61,15 +53,7 @@ describe("middleware-eventstream", () => {
         VideoWidth: "undefined",
         VideoHeight: "undefined",
         ChallengeVersions: "undefined",
-        LivenessRequestStream: {
-          [Symbol.asyncIterator]() {
-            return {
-              next() {
-                return this as any;
-              },
-            };
-          },
-        },
+        LivenessRequestStream: (async function* () {})(),
       });
 
       expect.assertions(2);
@@ -91,15 +75,7 @@ describe("middleware-eventstream", () => {
       await client.startStreamTranscription({
         MediaSampleRateHertz: 144,
         MediaEncoding: "ogg-opus",
-        AudioStream: {
-          [Symbol.asyncIterator]() {
-            return {
-              next() {
-                return this as any;
-              },
-            };
-          },
-        },
+        AudioStream: (async function* () {})(),
       });
 
       expect.assertions(2);
diff --git a/packages/middleware-websocket/src/middleware-websocket.integ.spec.ts b/packages/middleware-websocket/src/middleware-websocket.integ.spec.ts
index 7155b92c4979..26ce910f83f5 100644
--- a/packages/middleware-websocket/src/middleware-websocket.integ.spec.ts
+++ b/packages/middleware-websocket/src/middleware-websocket.integ.spec.ts
@@ -47,11 +47,7 @@ describe("middleware-websocket", () => {
         VideoWidth: "1024",
         VideoHeight: "1024",
         ChallengeVersions: "a,b,c",
-        LivenessRequestStream: {
-          [Symbol.asyncIterator]() {
-            return this as any;
-          },
-        },
+        LivenessRequestStream: (async function* () {})(),
       });
     });
   });