diff --git a/src/client/http_client.rs b/src/client/http_client.rs
index 80920701..f1c71279 100644
--- a/src/client/http_client.rs
+++ b/src/client/http_client.rs
@@ -582,9 +582,9 @@ impl BackupClient {
                     }
                     MergedChunkInfo::Known(chunk_list) => {
                         let mut digest_list = vec![];
-                        for chunk_info in chunk_list {
+                        for (_offset, digest) in chunk_list {
                             //println!("append existing chunk ({} bytes)", chunk_info.data.len());
-                            digest_list.push(tools::digest_to_hex(&chunk_info.digest));
+                            digest_list.push(tools::digest_to_hex(&digest));
                         }
                         println!("append existing chunks ({})", digest_list.len());
                         let param = json!({ "wid": wid, "digest-list": digest_list });
diff --git a/src/client/merge_known_chunks.rs b/src/client/merge_known_chunks.rs
index 8010302d..43c0ce02 100644
--- a/src/client/merge_known_chunks.rs
+++ b/src/client/merge_known_chunks.rs
@@ -10,7 +10,7 @@ pub struct ChunkInfo {
 }
 
 pub enum MergedChunkInfo {
-    Known(Vec<ChunkInfo>),
+    Known(Vec<(u64,[u8;32])>),
     New(ChunkInfo),
 }
 
@@ -65,11 +65,11 @@ impl <S> Stream for MergeKnownChunksQueue<S>
 
                         match last {
                             None => {
-                                self.buffer = Some(MergedChunkInfo::Known(vec![chunk_info]));
+                                self.buffer = Some(MergedChunkInfo::Known(vec![(chunk_info.offset, chunk_info.digest)]));
                                 // continue
                             }
                             Some(MergedChunkInfo::Known(mut list)) => {
-                                list.push(chunk_info);
+                                list.push((chunk_info.offset, chunk_info.digest));
                                 let len = list.len();
                                 self.buffer = Some(MergedChunkInfo::Known(list));
 
@@ -80,7 +80,7 @@ impl <S> Stream for MergeKnownChunksQueue<S>
 
                             }
                             Some(MergedChunkInfo::New(_)) => {
-                                self.buffer = Some(MergedChunkInfo::Known(vec![chunk_info]));
+                                self.buffer = Some(MergedChunkInfo::Known(vec![(chunk_info.offset, chunk_info.digest)]));
                                 return Ok(Async::Ready(last));
                             }
                         }