diff --git a/src/api2/admin/datastore/backup.rs b/src/api2/admin/datastore/backup.rs
index 2471eeb3..9f934e91 100644
--- a/src/api2/admin/datastore/backup.rs
+++ b/src/api2/admin/datastore/backup.rs
@@ -104,8 +104,9 @@ fn upgrade_to_backup_protocol(
                 let mut http = hyper::server::conn::Http::new();
                 http.http2_only(true);
                 // increase window size: todo - find optiomal size
-                http.http2_initial_stream_window_size( (1 << 31) - 2);
-                http.http2_initial_connection_window_size( (1 << 31) - 2);
+                let window_size = 32*1024*1024; // max = (1 << 31) - 2
+                http.http2_initial_stream_window_size(window_size);
+                http.http2_initial_connection_window_size(window_size);
 
                 http.serve_connection(conn, service)
                     .map_err(Error::from)
diff --git a/src/client/http_client.rs b/src/client/http_client.rs
index 3f78b2e3..ea66d33b 100644
--- a/src/client/http_client.rs
+++ b/src/client/http_client.rs
@@ -506,7 +506,7 @@ impl BackupClient {
         mpsc::Sender<(MergedChunkInfo, Option<h2::client::ResponseFuture>)>,
         sync::oneshot::Receiver<Result<(), Error>>
     ) {
-        let (verify_queue_tx, verify_queue_rx) = mpsc::channel(100);
+        let (verify_queue_tx, verify_queue_rx) = mpsc::channel(64);
         let (verify_result_tx, verify_result_rx) = sync::oneshot::channel();
 
         let h2_2 = h2.clone();
@@ -521,7 +521,7 @@ impl BackupClient {
                                 response
                                     .map_err(Error::from)
                                     .and_then(H2Client::h2api_response)
-                                    .and_then(move |result| {
+                                    .and_then(move |_result| {
                                         Ok(MergedChunkInfo::Known(list))
                                     })
                             )