diff --git a/app/vminsert/prompush/push.go b/app/vminsert/prompush/push.go
index 8333c8974..6291114f4 100644
--- a/app/vminsert/prompush/push.go
+++ b/app/vminsert/prompush/push.go
@@ -22,10 +22,19 @@ func Push(wr *prompbmarshal.WriteRequest) {
 	tss := wr.Timeseries
 	for len(tss) > 0 {
 		// Process big tss in smaller blocks in order to reduce maxmimum memory usage
+		samplesCount := 0
+		i := 0
+		for i < len(tss) {
+			samplesCount += len(tss[i].Samples)
+			i++
+			if samplesCount > maxRowsPerBlock {
+				break
+			}
+		}
 		tssBlock := tss
-		if len(tssBlock) > maxRowsPerBlock {
-			tssBlock = tss[:maxRowsPerBlock]
-			tss = tss[maxRowsPerBlock:]
+		if i < len(tss) {
+			tssBlock = tss[:i]
+			tss = tss[i:]
 		} else {
 			tss = nil
 		}
diff --git a/app/vminsert/promremotewrite/request_handler.go b/app/vminsert/promremotewrite/request_handler.go
index 27a7ffb6e..74568920c 100644
--- a/app/vminsert/promremotewrite/request_handler.go
+++ b/app/vminsert/promremotewrite/request_handler.go
@@ -50,14 +50,15 @@ func insertRows(timeseries []prompb.TimeSeries) error {
 		}
 		var metricNameRaw []byte
 		var err error
-		for i := range ts.Samples {
-			r := &ts.Samples[i]
+		samples := ts.Samples
+		for i := range samples {
+			r := &samples[i]
 			metricNameRaw, err = ctx.WriteDataPointExt(metricNameRaw, ctx.Labels, r.Timestamp, r.Value)
 			if err != nil {
 				return err
 			}
 		}
-		rowsTotal += len(ts.Samples)
+		rowsTotal += len(samples)
 	}
 	rowsInserted.Add(rowsTotal)
 	rowsPerInsert.Update(float64(rowsTotal))
diff --git a/app/vminsert/vmimport/request_handler.go b/app/vminsert/vmimport/request_handler.go
index c5ccac205..3094409ec 100644
--- a/app/vminsert/vmimport/request_handler.go
+++ b/app/vminsert/vmimport/request_handler.go
@@ -7,6 +7,7 @@ import (
 
 	"github.com/VictoriaMetrics/VictoriaMetrics/app/vminsert/common"
 	"github.com/VictoriaMetrics/VictoriaMetrics/app/vminsert/relabel"
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/logger"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/prompbmarshal"
 	parserCommon "github.com/VictoriaMetrics/VictoriaMetrics/lib/protoparser/common"
 	parser "github.com/VictoriaMetrics/VictoriaMetrics/lib/protoparser/vmimport"
@@ -68,7 +69,9 @@ func insertRows(rows []parser.Row, extraLabels []prompbmarshal.Label) error {
 		ctx.metricNameBuf = storage.MarshalMetricNameRaw(ctx.metricNameBuf[:0], ic.Labels)
 		values := r.Values
 		timestamps := r.Timestamps
-		_ = timestamps[len(values)-1]
+		if len(timestamps) != len(values) {
+			logger.Panicf("BUG: len(timestamps)=%d must match len(values)=%d", len(timestamps), len(values))
+		}
 		for j, value := range values {
 			timestamp := timestamps[j]
 			if err := ic.WriteDataPoint(ctx.metricNameBuf, nil, timestamp, value); err != nil {