diff --git a/model/value.go b/model/value.go
index 15a87570..f60675fa 100644
--- a/model/value.go
+++ b/model/value.go
@@ -98,11 +98,6 @@ func (s Sample) MarshalJSON() ([]byte, error) {
 	return json.Marshal(&v)
 }
 
-type sampleHistogramPairPtr struct {
-	Timestamp Time
-	Histogram *SampleHistogram
-}
-
 func (s *sampleHistogramPairPtr) UnmarshalJSON(buf []byte) error {
 	tmp := []interface{}{&s.Timestamp, &s.Histogram}
 	wantLen := len(tmp)
@@ -118,18 +113,18 @@ func (s *sampleHistogramPairPtr) UnmarshalJSON(buf []byte) error {
 // UnmarshalJSON implements json.Unmarshaler.
 func (s *Sample) UnmarshalJSON(b []byte) error {
 	v := struct {
-		Metric    Metric                 `json:"metric"`
-		Value     SamplePair             `json:"value"`
-		Histogram sampleHistogramPairPtr `json:"histogram"`
+		Metric    Metric               `json:"metric"`
+		Value     SamplePair           `json:"value"`
+		Histogram *SampleHistogramPair `json:"histogram"`
 	}{
 		Metric: s.Metric,
 		Value: SamplePair{
 			Timestamp: s.Timestamp,
 			Value:     s.Value,
 		},
-		Histogram: sampleHistogramPairPtr{
+		Histogram: &SampleHistogramPair{
 			Timestamp: s.Timestamp,
-			Histogram: s.Histogram,
+			Histogram: *s.Histogram,
 		},
 	}
 
@@ -138,9 +133,9 @@ func (s *Sample) UnmarshalJSON(b []byte) error {
 	}
 
 	s.Metric = v.Metric
-	if v.Histogram.Histogram != nil {
+	if v.Histogram != nil {
 		s.Timestamp = v.Histogram.Timestamp
-		s.Histogram = v.Histogram.Histogram
+		s.Histogram = &v.Histogram.Histogram
 	} else {
 		s.Timestamp = v.Value.Timestamp
 		s.Value = v.Value.Value