diff --git a/packages/react-dom/src/server/ReactDOMFizzServerBrowser.js b/packages/react-dom/src/server/ReactDOMFizzServerBrowser.js
index 1ae511ede561d..530139715e847 100644
--- a/packages/react-dom/src/server/ReactDOMFizzServerBrowser.js
+++ b/packages/react-dom/src/server/ReactDOMFizzServerBrowser.js
@@ -53,15 +53,19 @@ function renderToReadableStream(
     });
 
     function onShellReady() {
-      const stream: ReactDOMServerReadableStream = (new ReadableStream({
-        type: 'bytes',
-        pull(controller) {
-          startFlowing(request, controller);
+      const stream: ReactDOMServerReadableStream = (new ReadableStream(
+        {
+          type: 'bytes',
+          pull(controller) {
+            startFlowing(request, controller);
+          },
+          cancel(reason) {
+            abort(request);
+          },
         },
-        cancel(reason) {
-          abort(request);
-        },
-      }): any);
+        // $FlowFixMe size() methods are not allowed on byte streams.
+        {highWaterMark: 0},
+      ): any);
       // TODO: Move to sub-classing ReadableStream.
       stream.allReady = allReady;
       resolve(stream);
diff --git a/packages/react-server-dom-webpack/src/ReactFlightDOMServerBrowser.js b/packages/react-server-dom-webpack/src/ReactFlightDOMServerBrowser.js
index aeee2d24806db..a00eb8c441067 100644
--- a/packages/react-server-dom-webpack/src/ReactFlightDOMServerBrowser.js
+++ b/packages/react-server-dom-webpack/src/ReactFlightDOMServerBrowser.js
@@ -33,16 +33,20 @@ function renderToReadableStream(
     options ? options.onError : undefined,
     context,
   );
-  const stream = new ReadableStream({
-    type: 'bytes',
-    start(controller) {
-      startWork(request);
+  const stream = new ReadableStream(
+    {
+      type: 'bytes',
+      start(controller) {
+        startWork(request);
+      },
+      pull(controller) {
+        startFlowing(request, controller);
+      },
+      cancel(reason) {},
     },
-    pull(controller) {
-      startFlowing(request, controller);
-    },
-    cancel(reason) {},
-  });
+    // $FlowFixMe size() methods are not allowed on byte streams.
+    {highWaterMark: 0},
+  );
   return stream;
 }