diff --git a/pkgs/http_client_conformance_tests/lib/src/server_queue_helpers.dart b/pkgs/http_client_conformance_tests/lib/src/server_queue_helpers.dart
index 52a9b8781f..df87ddd177 100644
--- a/pkgs/http_client_conformance_tests/lib/src/server_queue_helpers.dart
+++ b/pkgs/http_client_conformance_tests/lib/src/server_queue_helpers.dart
@@ -5,5 +5,6 @@
 import 'package:async/async.dart';
 
 extension StreamQueueOfNullableObjectExtension on StreamQueue<Object?> {
+  /// When run under dart2wasm, JSON numbers are always returned as [double].
   Future<int> get nextAsInt async => ((await next) as num).toInt();
 }