diff --git a/packages/react-dom/src/server/ReactDOMFizzServerBrowser.js b/packages/react-dom/src/server/ReactDOMFizzServerBrowser.js
index b83e63236b302..530139715e847 100644
--- a/packages/react-dom/src/server/ReactDOMFizzServerBrowser.js
+++ b/packages/react-dom/src/server/ReactDOMFizzServerBrowser.js
@@ -63,10 +63,8 @@ function renderToReadableStream(
             abort(request);
           },
         },
-        {
-          highWaterMark: 0,
-          size: () => 1,
-        },
+        // $FlowFixMe size() methods are not allowed on byte streams.
+        {highWaterMark: 0},
       ): any);
       // TODO: Move to sub-classing ReadableStream.
       stream.allReady = allReady;
diff --git a/packages/react-server-dom-webpack/src/ReactFlightDOMServerBrowser.js b/packages/react-server-dom-webpack/src/ReactFlightDOMServerBrowser.js
index 78f1e9ce84d7f..a00eb8c441067 100644
--- a/packages/react-server-dom-webpack/src/ReactFlightDOMServerBrowser.js
+++ b/packages/react-server-dom-webpack/src/ReactFlightDOMServerBrowser.js
@@ -44,10 +44,8 @@ function renderToReadableStream(
       },
       cancel(reason) {},
     },
-    {
-      highWaterMark: 0,
-      size: () => 1,
-    },
+    // $FlowFixMe size() methods are not allowed on byte streams.
+    {highWaterMark: 0},
   );
   return stream;
 }