diff --git a/lib/storage/storage.go b/lib/storage/storage.go
index 58ed79c6c..ee590873d 100644
--- a/lib/storage/storage.go
+++ b/lib/storage/storage.go
@@ -1129,7 +1129,6 @@ func (s *Storage) add(rows []rawRow, mrs []MetricRow, precisionBits uint8) ([]ra
 		}
 	}
 	if pmrs != nil {
-		atomic.AddUint64(&s.slowRowInserts, uint64(len(pmrs.pmrs)))
 		// Sort pendingMetricRows by canonical metric name in order to speed up search via `is` in the loop below.
 		pendingMetricRows := pmrs.pmrs
 		sort.Slice(pendingMetricRows, func(i, j int) bool {
@@ -1137,6 +1136,7 @@ func (s *Storage) add(rows []rawRow, mrs []MetricRow, precisionBits uint8) ([]ra
 		})
 		is := idb.getIndexSearch(noDeadline)
 		prevMetricNameRaw = nil
+		var slowInsertsCount uint64
 		for i := range pendingMetricRows {
 			pmr := &pendingMetricRows[i]
 			mr := &pmr.mr
@@ -1160,6 +1160,7 @@ func (s *Storage) add(rows []rawRow, mrs []MetricRow, precisionBits uint8) ([]ra
 				prevMetricNameRaw = mr.MetricNameRaw
 				continue
 			}
+			slowInsertsCount++
 			if err := is.GetOrCreateTSIDByName(&r.TSID, pmr.MetricName); err != nil {
 				// Do not stop adding rows on error - just skip invalid row.
 				// This guarantees that invalid rows don't prevent
@@ -1174,6 +1175,7 @@ func (s *Storage) add(rows []rawRow, mrs []MetricRow, precisionBits uint8) ([]ra
 		}
 		idb.putIndexSearch(is)
 		putPendingMetricRows(pmrs)
+		atomic.AddUint64(&s.slowRowInserts, slowInsertsCount)
 	}
 	if firstWarn != nil {
 		logger.Errorf("warn occurred during rows addition: %s", firstWarn)