diff --git a/dio/lib/src/adapters/io_adapter.dart b/dio/lib/src/adapters/io_adapter.dart
index bffb07c6a..e7fd5de70 100644
--- a/dio/lib/src/adapters/io_adapter.dart
+++ b/dio/lib/src/adapters/io_adapter.dart
@@ -93,7 +93,7 @@ class IOHttpClientAdapter implements HttpClientAdapter {
       if (connectionTimeout != null && connectionTimeout > Duration.zero) {
         request = await reqFuture.timeout(
           connectionTimeout,
-          onTimeout: () async {
+          onTimeout: () {
             throw DioException.connectionTimeout(
               requestOptions: options,
               timeout: connectionTimeout,
@@ -147,12 +147,12 @@ class IOHttpClientAdapter implements HttpClientAdapter {
 
     if (requestStream != null) {
       // Transform the request data.
-      Future<void> future = request.addStream(requestStream);
+      Future<dynamic> future = request.addStream(requestStream);
       final sendTimeout = options.sendTimeout;
       if (sendTimeout != null && sendTimeout > Duration.zero) {
         future = future.timeout(
           sendTimeout,
-          onTimeout: () async {
+          onTimeout: () {
             request.abort();
             throw DioException.sendTimeout(
               timeout: sendTimeout,
@@ -169,7 +169,7 @@ class IOHttpClientAdapter implements HttpClientAdapter {
     if (receiveTimeout > Duration.zero) {
       future = future.timeout(
         receiveTimeout,
-        onTimeout: () async {
+        onTimeout: () {
           request.abort();
           throw DioException.receiveTimeout(
             timeout: receiveTimeout,
diff --git a/plugins/http2_adapter/lib/src/http2_adapter.dart b/plugins/http2_adapter/lib/src/http2_adapter.dart
index ae61eb8ca..ed6e8fa63 100644
--- a/plugins/http2_adapter/lib/src/http2_adapter.dart
+++ b/plugins/http2_adapter/lib/src/http2_adapter.dart
@@ -137,14 +137,14 @@ class Http2Adapter implements HttpClientAdapter {
     }
 
     if (hasRequestData) {
-      Future<void> requestStreamFuture = requestStream!.listen((data) {
+      Future<Uint8List> requestStreamFuture = requestStream!.listen((data) {
         stream.outgoingMessages.add(DataStreamMessage(data));
       }).asFuture();
       final sendTimeout = options.sendTimeout ?? Duration.zero;
       if (sendTimeout > Duration.zero) {
         requestStreamFuture = requestStreamFuture.timeout(
           sendTimeout,
-          onTimeout: () async {
+          onTimeout: () {
             stream.outgoingMessages.close().catchError((_) {});
             throw DioException.sendTimeout(
               timeout: sendTimeout,