diff --git a/internal/datanode/compaction/clustering_compactor.go b/internal/datanode/compaction/clustering_compactor.go
index 2a1d7ae7fa..0c5d43f152 100644
--- a/internal/datanode/compaction/clustering_compactor.go
+++ b/internal/datanode/compaction/clustering_compactor.go
@@ -831,6 +831,8 @@ func (t *clusteringCompactionTask) packBufferToSegment(ctx context.Context, buff
 		zap.Int64("segID", seg.GetSegmentID()),
 		zap.Int64("row num", seg.GetNumOfRows()))
 
+	// reset
+	buffer.flushedRowNum.Store(0)
 	// set old writer nil
 	writer = nil
 	return nil