diff --git a/observer/block_peer_common.go b/observer/block_peer_common.go
index 854d37c..1893808 100644
--- a/observer/block_peer_common.go
+++ b/observer/block_peer_common.go
@@ -193,9 +193,11 @@ func (bp *BlockPeer) initChannels(ctx context.Context) {
 func (bp *BlockPeer) getSeekFrom(channel string) SeekFromFetcher {
 	seekFrom := ChannelSeekOldest()
 	// at first check seekFrom var, if it is empty, check seekFromFetcher
+	bp.mu.Lock()
 	seekFromNum, exist := bp.seekFrom[channel]
+	bp.mu.Unlock()
 	if exist {
-		seekFrom = ChannelSeekFrom(seekFromNum)
+		seekFrom = ChannelSeekFrom(seekFromNum - 1)
 	} else {
 		// if seekFromFetcher is also empty, use ChannelSeekOldest
 		if bp.seekFromFetcher != nil {