diff --git a/pmtiles/makesync.go b/pmtiles/makesync.go
index bab39a0..d56602d 100644
--- a/pmtiles/makesync.go
+++ b/pmtiles/makesync.go
@@ -43,19 +43,15 @@ func SerializeSyncBlocks(output io.Writer, blocks []SyncBlock) {
 	var n int
 
 	lastStartId := uint64(0)
-	lastOffset := uint64(0)
 	for _, block := range blocks {
 		n = binary.PutUvarint(tmp, uint64(block.Start-lastStartId))
 		output.Write(tmp[:n])
-		n = binary.PutUvarint(tmp, uint64(block.Offset-lastOffset))
-		output.Write(tmp[:n])
 		n = binary.PutUvarint(tmp, uint64(block.Length))
 		output.Write(tmp[:n])
 		binary.LittleEndian.PutUint64(tmp, block.Hash)
 		output.Write(tmp[0:8])
 
 		lastStartId = block.Start
-		lastOffset = block.Offset
 	}
 }
 
@@ -63,18 +59,17 @@ func DeserializesyncBlocks(num_blocks int, reader *bufio.Reader) []SyncBlock {
 	blocks := make([]SyncBlock, 0)
 
 	lastStartId := uint64(0)
-	lastOffset := uint64(0)
+	offset := uint64(0)
 	buf := make([]byte, 8)
 
 	for i := 0; i < num_blocks; i++ {
 		start, _ := binary.ReadUvarint(reader)
-		offset, _ := binary.ReadUvarint(reader)
 		length, _ := binary.ReadUvarint(reader)
 		_, _ = io.ReadFull(reader, buf)
-		blocks = append(blocks, SyncBlock{Start: lastStartId + start, Offset: lastOffset + offset, Length: length, Hash: binary.LittleEndian.Uint64(buf)})
+		blocks = append(blocks, SyncBlock{Start: lastStartId + start, Offset: offset, Length: length, Hash: binary.LittleEndian.Uint64(buf)})
 
 		lastStartId = lastStartId + start
-		lastOffset = lastOffset + offset
+		offset = offset + length
 	}
 
 	return blocks