diff --git a/app/vmselect/promql/exec_test.go b/app/vmselect/promql/exec_test.go
index 4dc590400..2c7c2e405 100644
--- a/app/vmselect/promql/exec_test.go
+++ b/app/vmselect/promql/exec_test.go
@@ -2359,7 +2359,7 @@ func TestExecSuccess(t *testing.T) {
 		resultExpected := []netstorage.Result{r}
 		f(q, resultExpected)
 	})
-	t.Run(`histogram_quantile(nan-bucket-count)`, func(t *testing.T) {
+	t.Run(`histogram_quantile(nan-bucket-count-some)`, func(t *testing.T) {
 		t.Parallel()
 		q := `histogram_quantile(0.6,
 			label_set(90, "foo", "bar", "le", "10")
@@ -2368,7 +2368,7 @@ func TestExecSuccess(t *testing.T) {
 		)`
 		r := netstorage.Result{
 			MetricName: metricNameExpected,
-			Values:     []float64{30, 30, 30, 30, 30, 30},
+			Values:     []float64{10, 10, 10, 10, 10, 10},
 			Timestamps: timestampsExpected,
 		}
 		r.MetricName.Tags = []storage.Tag{{
@@ -2378,7 +2378,7 @@ func TestExecSuccess(t *testing.T) {
 		resultExpected := []netstorage.Result{r}
 		f(q, resultExpected)
 	})
-	t.Run(`histogram_quantile(nan-bucket-count)`, func(t *testing.T) {
+	t.Run(`histogram_quantile(normal-bucket-count)`, func(t *testing.T) {
 		t.Parallel()
 		q := `histogram_quantile(0.2,
 			label_set(0, "foo", "bar", "le", "10")
@@ -2407,7 +2407,7 @@ func TestExecSuccess(t *testing.T) {
 		resultExpected := []netstorage.Result{}
 		f(q, resultExpected)
 	})
-	t.Run(`histogram_quantile(nan-bucket-count)`, func(t *testing.T) {
+	t.Run(`histogram_quantile(nan-bucket-count-all)`, func(t *testing.T) {
 		t.Parallel()
 		q := `histogram_quantile(0.6,
 			label_set(nan, "foo", "bar", "le", "10")
@@ -2420,17 +2420,16 @@ func TestExecSuccess(t *testing.T) {
 	t.Run(`prometheus_buckets(missing-vmrange)`, func(t *testing.T) {
 		t.Parallel()
 		q := `sort(prometheus_buckets((
-			alias(label_set(90, "foo", "bar", "le", "0"), "xxx"),
 			alias(label_set(time()/20, "foo", "bar", "le", "0.2"), "xxx"),
 			alias(label_set(time()/100, "foo", "bar", "vmrange", "foobar"), "xxx"),
 			alias(label_set(time()/100, "foo", "bar", "vmrange", "30...foobar"), "xxx"),
 			alias(label_set(time()/100, "foo", "bar", "vmrange", "30...40"), "xxx"),
+			alias(label_set(time()/80, "foo", "bar", "vmrange", "0...900", "le", "54"), "yyy"),
 			alias(label_set(time()/40, "foo", "bar", "vmrange", "900...1000", "le", "2343"), "yyy"),
-			alias(label_set(time()/10, "foo", "bar", "vmrange", "1000...Inf", "le", "2343"), "yyy"),
 		)))`
 		r1 := netstorage.Result{
 			MetricName: metricNameExpected,
-			Values:     []float64{10, 12, 14, 16, 18, 20},
+			Values:     []float64{0, 0, 0, 0, 0, 0},
 			Timestamps: timestampsExpected,
 		}
 		r1.MetricName.MetricGroup = []byte("xxx")
@@ -2441,15 +2440,15 @@ func TestExecSuccess(t *testing.T) {
 			},
 			{
 				Key:   []byte("le"),
-				Value: []byte("40"),
+				Value: []byte("30"),
 			},
 		}
 		r2 := netstorage.Result{
 			MetricName: metricNameExpected,
-			Values:     []float64{25, 30, 35, 40, 45, 50},
+			Values:     []float64{10, 12, 14, 16, 18, 20},
 			Timestamps: timestampsExpected,
 		}
-		r2.MetricName.MetricGroup = []byte("yyy")
+		r2.MetricName.MetricGroup = []byte("xxx")
 		r2.MetricName.Tags = []storage.Tag{
 			{
 				Key:   []byte("foo"),
@@ -2457,12 +2456,12 @@ func TestExecSuccess(t *testing.T) {
 			},
 			{
 				Key:   []byte("le"),
-				Value: []byte("1000"),
+				Value: []byte("40"),
 			},
 		}
 		r3 := netstorage.Result{
 			MetricName: metricNameExpected,
-			Values:     []float64{125, 150, 175, 200, 225, 250},
+			Values:     []float64{12.5, 15, 17.5, 20, 22.5, 25},
 			Timestamps: timestampsExpected,
 		}
 		r3.MetricName.MetricGroup = []byte("yyy")
@@ -2473,19 +2472,51 @@ func TestExecSuccess(t *testing.T) {
 			},
 			{
 				Key:   []byte("le"),
-				Value: []byte("Inf"),
+				Value: []byte("900"),
 			},
 		}
-		resultExpected := []netstorage.Result{r1, r2, r3}
+		r4 := netstorage.Result{
+			MetricName: metricNameExpected,
+			Values:     []float64{37.5, 45, 52.5, 60, 67.5, 75},
+			Timestamps: timestampsExpected,
+		}
+		r4.MetricName.MetricGroup = []byte("yyy")
+		r4.MetricName.Tags = []storage.Tag{
+			{
+				Key:   []byte("foo"),
+				Value: []byte("bar"),
+			},
+			{
+				Key:   []byte("le"),
+				Value: []byte("1000"),
+			},
+		}
+		r5 := netstorage.Result{
+			MetricName: metricNameExpected,
+			Values:     []float64{50, 60, 70, 80, 90, 100},
+			Timestamps: timestampsExpected,
+		}
+		r5.MetricName.MetricGroup = []byte("xxx")
+		r5.MetricName.Tags = []storage.Tag{
+			{
+				Key:   []byte("foo"),
+				Value: []byte("bar"),
+			},
+			{
+				Key:   []byte("le"),
+				Value: []byte("0.2"),
+			},
+		}
+		resultExpected := []netstorage.Result{r1, r2, r3, r4, r5}
 		f(q, resultExpected)
 	})
 	t.Run(`prometheus_buckets(valid)`, func(t *testing.T) {
 		t.Parallel()
 		q := `sort(prometheus_buckets((
 			alias(label_set(90, "foo", "bar", "vmrange", "0...0"), "xxx"),
-			alias(label_set(time()/20, "foo", "bar", "vmrange", "0.1...0.2"), "xxx"),
-			alias(label_set(time()/100, "foo", "bar", "vmrange", "30...40"), "xxx"),
-			alias(label_set(time()/10, "foo", "bar", "vmrange", "1000...Inf"), "xxx"),
+			alias(label_set(time()/20, "foo", "bar", "vmrange", "0...0.2"), "xxx"),
+			alias(label_set(time()/100, "foo", "bar", "vmrange", "0.2...40"), "xxx"),
+			alias(label_set(time()/10, "foo", "bar", "vmrange", "40...Inf"), "xxx"),
 		)))`
 		r1 := netstorage.Result{
 			MetricName: metricNameExpected,
@@ -4424,12 +4455,12 @@ func testResultsEqual(t *testing.T, result, resultExpected []netstorage.Result)
 	for i := range result {
 		r := &result[i]
 		rExpected := &resultExpected[i]
-		testMetricNamesEqual(t, &r.MetricName, &rExpected.MetricName)
+		testMetricNamesEqual(t, &r.MetricName, &rExpected.MetricName, i)
 		testRowsEqual(t, r.Values, r.Timestamps, rExpected.Values, rExpected.Timestamps)
 	}
 }
 
-func testMetricNamesEqual(t *testing.T, mn, mnExpected *storage.MetricName) {
+func testMetricNamesEqual(t *testing.T, mn, mnExpected *storage.MetricName, pos int) {
 	t.Helper()
 	if mn.AccountID != mnExpected.AccountID {
 		t.Fatalf(`unexpected accountID; got %d; want %d`, mn.AccountID, mnExpected.AccountID)
@@ -4438,19 +4469,19 @@ func testMetricNamesEqual(t *testing.T, mn, mnExpected *storage.MetricName) {
 		t.Fatalf(`unexpected projectID; got %d; want %d`, mn.ProjectID, mnExpected.ProjectID)
 	}
 	if string(mn.MetricGroup) != string(mnExpected.MetricGroup) {
-		t.Fatalf(`unexpected MetricGroup; got %q; want %q`, mn.MetricGroup, mnExpected.MetricGroup)
+		t.Fatalf(`unexpected MetricGroup at #%d; got %q; want %q`, pos, mn.MetricGroup, mnExpected.MetricGroup)
 	}
 	if len(mn.Tags) != len(mnExpected.Tags) {
-		t.Fatalf(`unexpected tags count; got %d; want %d`, len(mn.Tags), len(mnExpected.Tags))
+		t.Fatalf(`unexpected tags count at #%d; got %d; want %d`, pos, len(mn.Tags), len(mnExpected.Tags))
 	}
 	for i := range mn.Tags {
 		tag := &mn.Tags[i]
 		tagExpected := &mnExpected.Tags[i]
 		if string(tag.Key) != string(tagExpected.Key) {
-			t.Fatalf(`unexpected tag key; got %q; want %q`, tag.Key, tagExpected.Key)
+			t.Fatalf(`unexpected tag key at #%d,%d; got %q; want %q`, pos, i, tag.Key, tagExpected.Key)
 		}
 		if string(tag.Value) != string(tagExpected.Value) {
-			t.Fatalf(`unexpected tag value; got %q; want %q`, tag.Value, tagExpected.Value)
+			t.Fatalf(`unexpected tag value at #%d,%d; got %q; want %q`, pos, i, tag.Value, tagExpected.Value)
 		}
 	}
 }
diff --git a/app/vmselect/promql/rollup_result_cache_test.go b/app/vmselect/promql/rollup_result_cache_test.go
index 998d66de9..26e7b2e3d 100644
--- a/app/vmselect/promql/rollup_result_cache_test.go
+++ b/app/vmselect/promql/rollup_result_cache_test.go
@@ -394,7 +394,7 @@ func testTimeseriesEqual(t *testing.T, tss, tssExpected []*timeseries) {
 	}
 	for i, ts := range tss {
 		tsExpected := tssExpected[i]
-		testMetricNamesEqual(t, &ts.MetricName, &tsExpected.MetricName)
+		testMetricNamesEqual(t, &ts.MetricName, &tsExpected.MetricName, i)
 		testRowsEqual(t, ts.Values, ts.Timestamps, tsExpected.Values, tsExpected.Timestamps)
 	}
 }
diff --git a/app/vmselect/promql/transform.go b/app/vmselect/promql/transform.go
index 33c950b01..445462846 100644
--- a/app/vmselect/promql/transform.go
+++ b/app/vmselect/promql/transform.go
@@ -278,42 +278,85 @@ func transformPrometheusBuckets(tfa *transformFuncArg) ([]*timeseries, error) {
 	if err := expectTransformArgsNum(args, 1); err != nil {
 		return nil, err
 	}
+	rvs := vmrangeBucketsToLE(args[0])
+	return rvs, nil
+}
+
+func vmrangeBucketsToLE(tss []*timeseries) []*timeseries {
+	rvs := make([]*timeseries, 0, len(tss))
 
 	// Group timeseries by MetricGroup+tags excluding `vmrange` tag.
 	type x struct {
-		leStr string
-		le    float64
-		ts    *timeseries
+		startStr string
+		endStr   string
+		start    float64
+		end      float64
+		ts       *timeseries
 	}
 	m := make(map[string][]x)
 	bb := bbPool.Get()
 	defer bbPool.Put(bb)
-	for _, ts := range args[0] {
+	for _, ts := range tss {
 		vmrange := ts.MetricName.GetTagValue("vmrange")
 		if len(vmrange) == 0 {
+			if le := ts.MetricName.GetTagValue("le"); len(le) > 0 {
+				// Keep Prometheus-compatible buckets.
+				rvs = append(rvs, ts)
+			}
 			continue
 		}
 		n := strings.Index(bytesutil.ToUnsafeString(vmrange), "...")
 		if n < 0 {
 			continue
 		}
-		leStr := string(vmrange[n+len("..."):])
-		le, err := strconv.ParseFloat(leStr, 64)
+		startStr := string(vmrange[:n])
+		start, err := strconv.ParseFloat(startStr, 64)
 		if err != nil {
 			continue
 		}
+		endStr := string(vmrange[n+len("..."):])
+		end, err := strconv.ParseFloat(endStr, 64)
+		if err != nil {
+			continue
+		}
+		ts.MetricName.RemoveTag("le")
 		ts.MetricName.RemoveTag("vmrange")
 		bb.B = marshalMetricNameSorted(bb.B[:0], &ts.MetricName)
 		m[string(bb.B)] = append(m[string(bb.B)], x{
-			leStr: leStr,
-			le:    le,
-			ts:    ts,
+			startStr: startStr,
+			endStr:   endStr,
+			start:    start,
+			end:      end,
+			ts:       ts,
 		})
 	}
 
-	rvs := make([]*timeseries, 0, len(args[0]))
+	// Convert `vmrange` label in each group of time series to `le` label.
 	for _, xss := range m {
-		sort.Slice(xss, func(i, j int) bool { return xss[i].le < xss[j].le })
+		sort.Slice(xss, func(i, j int) bool { return xss[i].end < xss[j].end })
+		xssNew := make([]x, 0, len(xss))
+		endStrPrev := "0"
+		for _, xs := range xss {
+			ts := xs.ts
+			if xs.startStr != endStrPrev {
+				var tsDummy timeseries
+				tsDummy.CopyFromShallowTimestamps(ts)
+				values := tsDummy.Values
+				for i := range values {
+					values[i] = 0
+				}
+				tsDummy.MetricName.AddTag("le", xs.startStr)
+				xssNew = append(xssNew, x{
+					endStr: xs.startStr,
+					end:    xs.start,
+					ts:     &tsDummy,
+				})
+			}
+			ts.MetricName.AddTag("le", xs.endStr)
+			xssNew = append(xssNew, xs)
+			endStrPrev = xs.endStr
+		}
+		xss = xssNew
 		for i := range xss[0].ts.Values {
 			count := float64(0)
 			for _, xs := range xss {
@@ -322,16 +365,14 @@ func transformPrometheusBuckets(tfa *transformFuncArg) ([]*timeseries, error) {
 				if !math.IsNaN(v) {
 					count += v
 				}
-				ts.MetricName.RemoveTag("le")
-				ts.MetricName.AddTag("le", xs.leStr)
 				ts.Values[i] = count
 			}
 		}
-		for i := range xss {
-			rvs = append(rvs, xss[i].ts)
+		for _, xs := range xss {
+			rvs = append(rvs, xs.ts)
 		}
 	}
-	return rvs, nil
+	return rvs
 }
 
 func transformHistogramQuantile(tfa *transformFuncArg) ([]*timeseries, error) {
@@ -344,6 +385,9 @@ func transformHistogramQuantile(tfa *transformFuncArg) ([]*timeseries, error) {
 		return nil, err
 	}
 
+	// Convert buckets with `vmrange` labels to buckets with `le` labels.
+	tss := vmrangeBucketsToLE(args[1])
+
 	// Group metrics by all tags excluding "le"
 	type x struct {
 		le float64
@@ -351,7 +395,7 @@ func transformHistogramQuantile(tfa *transformFuncArg) ([]*timeseries, error) {
 	}
 	m := make(map[string][]x)
 	bb := bbPool.Get()
-	for _, ts := range args[1] {
+	for _, ts := range tss {
 		tagValue := ts.MetricName.GetTagValue("le")
 		if len(tagValue) == 0 {
 			continue
@@ -375,18 +419,16 @@ func transformHistogramQuantile(tfa *transformFuncArg) ([]*timeseries, error) {
 	lastNonInf := func(i int, xss []x) float64 {
 		for len(xss) > 0 {
 			xsLast := xss[len(xss)-1]
-			if xsLast.ts.Values[i] == 0 {
+			v := xsLast.ts.Values[i]
+			if v == 0 {
 				return nan
 			}
-			if !math.IsInf(xsLast.le, 0) {
-				break
+			if !math.IsNaN(v) && !math.IsInf(xsLast.le, 0) {
+				return xsLast.le
 			}
 			xss = xss[:len(xss)-1]
 		}
-		if len(xss) == 0 {
-			return nan
-		}
-		return xss[len(xss)-1].le
+		return nan
 	}
 	quantile := func(i int, phis []float64, xss []x) float64 {
 		phi := phis[i]
@@ -399,9 +441,9 @@ func transformHistogramQuantile(tfa *transformFuncArg) ([]*timeseries, error) {
 		vPrev := float64(0)
 		for _, xs := range xss {
 			v := xs.ts.Values[i]
-			if math.IsNaN(v) || v < vPrev {
+			if v < vPrev {
 				xs.ts.Values[i] = vPrev
-			} else {
+			} else if !math.IsNaN(v) {
 				vPrev = v
 			}
 		}
@@ -423,6 +465,11 @@ func transformHistogramQuantile(tfa *transformFuncArg) ([]*timeseries, error) {
 		lePrev := float64(0)
 		for _, xs := range xss {
 			v := xs.ts.Values[i]
+			if math.IsNaN(v) {
+				// Skip NaNs - they may appear if the selected time range
+				// contains multiple different bucket sets.
+				continue
+			}
 			le := xs.le
 			if v < vReq {
 				vPrev = v
@@ -450,7 +497,6 @@ func transformHistogramQuantile(tfa *transformFuncArg) ([]*timeseries, error) {
 		}
 		rvs = append(rvs, dst)
 	}
-
 	return rvs, nil
 }