diff --git a/prompb/io/prometheus/client/metrics.pb.go b/prompb/io/prometheus/client/metrics.pb.go
index 2e7f7b390..48f68ec19 100644
--- a/prompb/io/prometheus/client/metrics.pb.go
+++ b/prompb/io/prometheus/client/metrics.pb.go
@@ -28,11 +28,18 @@ const _ = proto.GoGoProtoPackageIsVersion3 // please upgrade the proto package
 type MetricType int32
 
 const (
-	MetricType_COUNTER   MetricType = 0
-	MetricType_GAUGE     MetricType = 1
-	MetricType_SUMMARY   MetricType = 2
-	MetricType_UNTYPED   MetricType = 3
+	// COUNTER must use the Metric field "counter".
+	MetricType_COUNTER MetricType = 0
+	// GAUGE must use the Metric field "gauge".
+	MetricType_GAUGE MetricType = 1
+	// SUMMARY must use the Metric field "summary".
+	MetricType_SUMMARY MetricType = 2
+	// UNTYPED must use the Metric field "untyped".
+	MetricType_UNTYPED MetricType = 3
+	// HISTOGRAM must use the Metric field "histogram".
 	MetricType_HISTOGRAM MetricType = 4
+	// GAUGE_HISTOGRAM must use the Metric field "histogram".
+	MetricType_GAUGE_HISTOGRAM MetricType = 5
 )
 
 var MetricType_name = map[int32]string{
@@ -41,14 +48,16 @@ var MetricType_name = map[int32]string{
 	2: "SUMMARY",
 	3: "UNTYPED",
 	4: "HISTOGRAM",
+	5: "GAUGE_HISTOGRAM",
 }
 
 var MetricType_value = map[string]int32{
-	"COUNTER":   0,
-	"GAUGE":     1,
-	"SUMMARY":   2,
-	"UNTYPED":   3,
-	"HISTOGRAM": 4,
+	"COUNTER":         0,
+	"GAUGE":           1,
+	"SUMMARY":         2,
+	"UNTYPED":         3,
+	"HISTOGRAM":       4,
+	"GAUGE_HISTOGRAM": 5,
 }
 
 func (x MetricType) String() string {
@@ -382,9 +391,10 @@ func (m *Untyped) GetValue() float64 {
 }
 
 type Histogram struct {
-	SampleCount uint64    `protobuf:"varint,1,opt,name=sample_count,json=sampleCount,proto3" json:"sample_count,omitempty"`
-	SampleSum   float64   `protobuf:"fixed64,2,opt,name=sample_sum,json=sampleSum,proto3" json:"sample_sum,omitempty"`
-	Bucket      []*Bucket `protobuf:"bytes,3,rep,name=bucket,proto3" json:"bucket,omitempty"`
+	SampleCount      uint64    `protobuf:"varint,1,opt,name=sample_count,json=sampleCount,proto3" json:"sample_count,omitempty"`
+	SampleCountFloat float64   `protobuf:"fixed64,9,opt,name=sample_count_float,json=sampleCountFloat,proto3" json:"sample_count_float,omitempty"`
+	SampleSum        float64   `protobuf:"fixed64,2,opt,name=sample_sum,json=sampleSum,proto3" json:"sample_sum,omitempty"`
+	Bucket           []*Bucket `protobuf:"bytes,3,rep,name=bucket,proto3" json:"bucket,omitempty"`
 	// Sparse bucket (sb) stuff:
 	// The sb_schema defines the bucket schema. Currently, valid numbers are -4 <= n <= 8.
 	// They are all for base-2 bucket schemas, where 1 is a bucket boundary in each case, and
@@ -394,6 +404,7 @@ type Histogram struct {
 	SbSchema             int32          `protobuf:"zigzag32,4,opt,name=sb_schema,json=sbSchema,proto3" json:"sb_schema,omitempty"`
 	SbZeroThreshold      float64        `protobuf:"fixed64,5,opt,name=sb_zero_threshold,json=sbZeroThreshold,proto3" json:"sb_zero_threshold,omitempty"`
 	SbZeroCount          uint64         `protobuf:"varint,6,opt,name=sb_zero_count,json=sbZeroCount,proto3" json:"sb_zero_count,omitempty"`
+	SbZeroCountFloat     float64        `protobuf:"fixed64,10,opt,name=sb_zero_count_float,json=sbZeroCountFloat,proto3" json:"sb_zero_count_float,omitempty"`
 	SbNegative           *SparseBuckets `protobuf:"bytes,7,opt,name=sb_negative,json=sbNegative,proto3" json:"sb_negative,omitempty"`
 	SbPositive           *SparseBuckets `protobuf:"bytes,8,opt,name=sb_positive,json=sbPositive,proto3" json:"sb_positive,omitempty"`
 	XXX_NoUnkeyedLiteral struct{}       `json:"-"`
@@ -441,6 +452,13 @@ func (m *Histogram) GetSampleCount() uint64 {
 	return 0
 }
 
+func (m *Histogram) GetSampleCountFloat() float64 {
+	if m != nil {
+		return m.SampleCountFloat
+	}
+	return 0
+}
+
 func (m *Histogram) GetSampleSum() float64 {
 	if m != nil {
 		return m.SampleSum
@@ -476,6 +494,13 @@ func (m *Histogram) GetSbZeroCount() uint64 {
 	return 0
 }
 
+func (m *Histogram) GetSbZeroCountFloat() float64 {
+	if m != nil {
+		return m.SbZeroCountFloat
+	}
+	return 0
+}
+
 func (m *Histogram) GetSbNegative() *SparseBuckets {
 	if m != nil {
 		return m.SbNegative
@@ -492,6 +517,7 @@ func (m *Histogram) GetSbPositive() *SparseBuckets {
 
 type Bucket struct {
 	CumulativeCount      uint64    `protobuf:"varint,1,opt,name=cumulative_count,json=cumulativeCount,proto3" json:"cumulative_count,omitempty"`
+	CumulativeCountFloat float64   `protobuf:"fixed64,4,opt,name=cumulative_count_float,json=cumulativeCountFloat,proto3" json:"cumulative_count_float,omitempty"`
 	UpperBound           float64   `protobuf:"fixed64,2,opt,name=upper_bound,json=upperBound,proto3" json:"upper_bound,omitempty"`
 	Exemplar             *Exemplar `protobuf:"bytes,3,opt,name=exemplar,proto3" json:"exemplar,omitempty"`
 	XXX_NoUnkeyedLiteral struct{}  `json:"-"`
@@ -539,6 +565,13 @@ func (m *Bucket) GetCumulativeCount() uint64 {
 	return 0
 }
 
+func (m *Bucket) GetCumulativeCountFloat() float64 {
+	if m != nil {
+		return m.CumulativeCountFloat
+	}
+	return 0
+}
+
 func (m *Bucket) GetUpperBound() float64 {
 	if m != nil {
 		return m.UpperBound
@@ -554,11 +587,14 @@ func (m *Bucket) GetExemplar() *Exemplar {
 }
 
 type SparseBuckets struct {
-	Span                 []*SparseBuckets_Span `protobuf:"bytes,1,rep,name=span,proto3" json:"span,omitempty"`
-	Delta                []int64               `protobuf:"zigzag64,2,rep,packed,name=delta,proto3" json:"delta,omitempty"`
-	XXX_NoUnkeyedLiteral struct{}              `json:"-"`
-	XXX_unrecognized     []byte                `json:"-"`
-	XXX_sizecache        int32                 `json:"-"`
+	Span []*SparseBuckets_Span `protobuf:"bytes,1,rep,name=span,proto3" json:"span,omitempty"`
+	// Only one of "delta" or "count" may be used, the former for regular
+	// histograms with integer counts, the latter for float histograms.
+	Delta                []int64   `protobuf:"zigzag64,2,rep,packed,name=delta,proto3" json:"delta,omitempty"`
+	Count                []float64 `protobuf:"fixed64,3,rep,packed,name=count,proto3" json:"count,omitempty"`
+	XXX_NoUnkeyedLiteral struct{}  `json:"-"`
+	XXX_unrecognized     []byte    `json:"-"`
+	XXX_sizecache        int32     `json:"-"`
 }
 
 func (m *SparseBuckets) Reset()         { *m = SparseBuckets{} }
@@ -608,6 +644,19 @@ func (m *SparseBuckets) GetDelta() []int64 {
 	return nil
 }
 
+func (m *SparseBuckets) GetCount() []float64 {
+	if m != nil {
+		return m.Count
+	}
+	return nil
+}
+
+// A Span is a given number of consecutive buckets at a given
+// offset. Logically, it would be more straightforward to include
+// the bucket counts in the Span. However, the protobuf
+// representation is more compact in the way the data is structured
+// here (with all the buckets in a single array separate from the
+// Spans).
 type SparseBuckets_Span struct {
 	Offset               int32    `protobuf:"zigzag32,1,opt,name=offset,proto3" json:"offset,omitempty"`
 	Length               uint32   `protobuf:"varint,2,opt,name=length,proto3" json:"length,omitempty"`
@@ -914,60 +963,65 @@ func init() {
 }
 
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+	0x81, 0xcf, 0x67, 0x0b, 0x1a, 0x13, 0xd7, 0xee, 0x5b, 0x87, 0xdb, 0xb8, 0xc3, 0x83, 0xb1, 0xaa,
+	0xd1, 0x3d, 0xd8, 0xe6, 0x81, 0xff, 0x13, 0xcd, 0x98, 0x2f, 0x16, 0x19, 0xe5, 0x0b, 0x16, 0x5d,
+	0xba, 0x4d, 0xf5, 0xe0, 0x2d, 0x1e, 0xbc, 0xa0, 0x19, 0x9b, 0x14, 0x6d, 0xe4, 0xc1, 0x66, 0x81,
+	0xd5, 0x7e, 0x5b, 0xc6, 0xaf, 0xc2, 0x69, 0xbf, 0x1f, 0xc3, 0xed, 0x15, 0x8c, 0x31, 0x0c, 0xc6,
+	0x70, 0x85, 0xd4, 0x86, 0x1f, 0x43, 0x97, 0x07, 0x7e, 0x42, 0xe7, 0x44, 0x84, 0x2f, 0xa9, 0xdb,
+	0x56, 0xe7, 0xee, 0x83, 0x7a, 0x5b, 0xe3, 0x94, 0x64, 0x9c, 0x6a, 0x73, 0x1c, 0x03, 0x0f, 0xce,
+	0x0d, 0xcd, 0x4c, 0x49, 0x19, 0x0f, 0xd5, 0x94, 0xce, 0x1b, 0x4d, 0xb9, 0x30, 0x34, 0xef, 0x77,
+	0x0b, 0x5a, 0xba, 0x8f, 0x3e, 0x84, 0xde, 0x2c, 0x8f, 0xf3, 0x48, 0x8d, 0x5f, 0x79, 0xb9, 0x5b,
+	0x55, 0x5f, 0x1b, 0x3e, 0x82, 0x3b, 0xaf, 0x42, 0x8d, 0x67, 0x5b, 0x79, 0xde, 0x79, 0x85, 0xa0,
+	0x7d, 0x1f, 0x40, 0x37, 0x4f, 0x53, 0x9a, 0xf9, 0x01, 0xcb, 0x93, 0x4b, 0xf3, 0xa6, 0x41, 0xb5,
+	0x4e, 0x64, 0x67, 0xe5, 0x36, 0x36, 0xde, 0xf0, 0x36, 0xfe, 0x66, 0xc1, 0xe6, 0x8a, 0x4d, 0xf4,
+	0x10, 0x6c, 0x9e, 0x92, 0xc4, 0xb5, 0xd4, 0xb1, 0x39, 0x7c, 0x8d, 0xcd, 0xc8, 0x2a, 0xc1, 0x8a,
+	0x25, 0xaf, 0xc2, 0x25, 0x8d, 0x04, 0x71, 0x37, 0xfa, 0x8d, 0x43, 0x84, 0x75, 0x21, 0xbb, 0x7a,
+	0x31, 0xf2, 0x2c, 0x5a, 0x58, 0x17, 0xbb, 0x9f, 0x81, 0x2d, 0x99, 0xe8, 0x0e, 0xb4, 0xd8, 0xd5,
+	0x15, 0xa7, 0x7a, 0x6f, 0xdb, 0xd8, 0x54, 0xb2, 0x1f, 0xd1, 0x64, 0x2e, 0x16, 0xca, 0xf3, 0x26,
+	0x36, 0x95, 0xf7, 0x8b, 0x05, 0x9d, 0xc2, 0x0a, 0x7a, 0x00, 0xcd, 0x48, 0x26, 0xa0, 0xd1, 0x7b,
+	0x50, 0xaf, 0xb7, 0x0c, 0x49, 0xac, 0xd1, 0xf5, 0xe9, 0x82, 0xbe, 0x00, 0xa7, 0x4c, 0x58, 0xb3,
+	0xca, 0xdd, 0x81, 0xce, 0xe0, 0x41, 0x91, 0xc1, 0x83, 0x49, 0x81, 0xc0, 0x15, 0xd8, 0xfb, 0x67,
+	0x03, 0x5a, 0x23, 0x95, 0xe8, 0x6f, 0xab, 0xe8, 0x13, 0x68, 0xce, 0x65, 0x26, 0x9b, 0x40, 0xbd,
+	0x5b, 0x4f, 0x53, 0xb1, 0x8d, 0x35, 0x12, 0x7d, 0x0e, 0xed, 0x99, 0xce, 0x69, 0x23, 0x76, 0xaf,
+	0x9e, 0x64, 0xc2, 0x1c, 0x17, 0x68, 0x49, 0xe4, 0x3a, 0x44, 0xd5, 0xc9, 0x5b, 0x4b, 0x34, 0x49,
+	0x8b, 0x0b, 0xb4, 0x24, 0xe6, 0x3a, 0xf4, 0xd4, 0xc5, 0x5f, 0x4b, 0x34, 0xc9, 0x88, 0x0b, 0x34,
+	0xfa, 0x0a, 0x9c, 0x45, 0x91, 0x85, 0xe6, 0xea, 0xae, 0x59, 0x4c, 0x19, 0x99, 0xb8, 0x62, 0xc8,
+	0xf4, 0x2c, 0x77, 0xed, 0xc7, 0x5c, 0xa5, 0x49, 0x03, 0x77, 0xcb, 0xde, 0x88, 0x7b, 0xbf, 0x5a,
+	0x70, 0x4b, 0xbf, 0x81, 0x27, 0x24, 0x0e, 0xa3, 0x65, 0xed, 0xe7, 0x10, 0x81, 0xbd, 0xa0, 0x51,
+	0x6a, 0xbe, 0x86, 0xea, 0x37, 0x3a, 0x02, 0x5b, 0x6a, 0x54, 0x2b, 0x7c, 0xf7, 0x7e, 0xbf, 0x5e,
+	0x95, 0x9e, 0x3c, 0x59, 0xa6, 0x14, 0x2b, 0xb4, 0xcc, 0x57, 0xfd, 0x05, 0x77, 0xed, 0xff, 0xca,
+	0x57, 0xcd, 0xc3, 0x06, 0x7b, 0x2f, 0x00, 0xa8, 0x26, 0xa1, 0x2e, 0xb4, 0x1f, 0x3d, 0x9b, 0x9e,
+	0x4f, 0x4e, 0x71, 0xef, 0x1d, 0xe4, 0x40, 0xf3, 0xec, 0x78, 0x7a, 0x76, 0xda, 0xb3, 0x64, 0x7f,
+	0x3c, 0x1d, 0x8d, 0x8e, 0xf1, 0xf3, 0xde, 0x86, 0x2c, 0xa6, 0xe7, 0x93, 0xe7, 0x17, 0xa7, 0x8f,
+	0x7b, 0x0d, 0xb4, 0x09, 0xce, 0xd3, 0xaf, 0xc7, 0x93, 0x67, 0x67, 0xf8, 0x78, 0xd4, 0xb3, 0xd1,
+	0x6d, 0xd8, 0x52, 0x1c, 0xbf, 0x6a, 0x36, 0x4f, 0xbc, 0x3f, 0xae, 0xf7, 0xad, 0x3f, 0xaf, 0xf7,
+	0xad, 0xbf, 0xaf, 0xf7, 0xad, 0x17, 0x3b, 0x21, 0xf3, 0x2b, 0x59, 0xbe, 0x96, 0x15, 0xb4, 0xd4,
+	0x69, 0xfe, 0xf4, 0xdf, 0x00, 0x00, 0x00, 0xff, 0xff, 0x06, 0x77, 0x31, 0x97, 0x9b, 0x08, 0x00,
+	0x00,
 }
 
 func (m *LabelPair) Marshal() (dAtA []byte, err error) {
@@ -1237,6 +1291,18 @@ func (m *Histogram) MarshalToSizedBuffer(dAtA []byte) (int, error) {
 		i -= len(m.XXX_unrecognized)
 		copy(dAtA[i:], m.XXX_unrecognized)
 	}
+	if m.SbZeroCountFloat != 0 {
+		i -= 8
+		encoding_binary.LittleEndian.PutUint64(dAtA[i:], uint64(math.Float64bits(float64(m.SbZeroCountFloat))))
+		i--
+		dAtA[i] = 0x51
+	}
+	if m.SampleCountFloat != 0 {
+		i -= 8
+		encoding_binary.LittleEndian.PutUint64(dAtA[i:], uint64(math.Float64bits(float64(m.SampleCountFloat))))
+		i--
+		dAtA[i] = 0x49
+	}
 	if m.SbPositive != nil {
 		{
 			size, err := m.SbPositive.MarshalToSizedBuffer(dAtA[:i])
@@ -1329,6 +1395,12 @@ func (m *Bucket) MarshalToSizedBuffer(dAtA []byte) (int, error) {
 		i -= len(m.XXX_unrecognized)
 		copy(dAtA[i:], m.XXX_unrecognized)
 	}
+	if m.CumulativeCountFloat != 0 {
+		i -= 8
+		encoding_binary.LittleEndian.PutUint64(dAtA[i:], uint64(math.Float64bits(float64(m.CumulativeCountFloat))))
+		i--
+		dAtA[i] = 0x21
+	}
 	if m.Exemplar != nil {
 		{
 			size, err := m.Exemplar.MarshalToSizedBuffer(dAtA[:i])
@@ -1379,22 +1451,32 @@ func (m *SparseBuckets) MarshalToSizedBuffer(dAtA []byte) (int, error) {
 		i -= len(m.XXX_unrecognized)
 		copy(dAtA[i:], m.XXX_unrecognized)
 	}
-	if len(m.Delta) > 0 {
-		var j5 int
-		dAtA7 := make([]byte, len(m.Delta)*10)
-		for _, num := range m.Delta {
-			x6 := (uint64(num) << 1) ^ uint64((num >> 63))
-			for x6 >= 1<<7 {
-				dAtA7[j5] = uint8(uint64(x6)&0x7f | 0x80)
-				j5++
-				x6 >>= 7
-			}
-			dAtA7[j5] = uint8(x6)
-			j5++
+	if len(m.Count) > 0 {
+		for iNdEx := len(m.Count) - 1; iNdEx >= 0; iNdEx-- {
+			f5 := math.Float64bits(float64(m.Count[iNdEx]))
+			i -= 8
+			encoding_binary.LittleEndian.PutUint64(dAtA[i:], uint64(f5))
 		}
-		i -= j5
-		copy(dAtA[i:], dAtA7[:j5])
-		i = encodeVarintMetrics(dAtA, i, uint64(j5))
+		i = encodeVarintMetrics(dAtA, i, uint64(len(m.Count)*8))
+		i--
+		dAtA[i] = 0x1a
+	}
+	if len(m.Delta) > 0 {
+		var j6 int
+		dAtA8 := make([]byte, len(m.Delta)*10)
+		for _, num := range m.Delta {
+			x7 := (uint64(num) << 1) ^ uint64((num >> 63))
+			for x7 >= 1<<7 {
+				dAtA8[j6] = uint8(uint64(x7)&0x7f | 0x80)
+				j6++
+				x7 >>= 7
+			}
+			dAtA8[j6] = uint8(x7)
+			j6++
+		}
+		i -= j6
+		copy(dAtA[i:], dAtA8[:j6])
+		i = encodeVarintMetrics(dAtA, i, uint64(j6))
 		i--
 		dAtA[i] = 0x12
 	}
@@ -1834,6 +1916,12 @@ func (m *Histogram) Size() (n int) {
 		l = m.SbPositive.Size()
 		n += 1 + l + sovMetrics(uint64(l))
 	}
+	if m.SampleCountFloat != 0 {
+		n += 9
+	}
+	if m.SbZeroCountFloat != 0 {
+		n += 9
+	}
 	if m.XXX_unrecognized != nil {
 		n += len(m.XXX_unrecognized)
 	}
@@ -1856,6 +1944,9 @@ func (m *Bucket) Size() (n int) {
 		l = m.Exemplar.Size()
 		n += 1 + l + sovMetrics(uint64(l))
 	}
+	if m.CumulativeCountFloat != 0 {
+		n += 9
+	}
 	if m.XXX_unrecognized != nil {
 		n += len(m.XXX_unrecognized)
 	}
@@ -1881,6 +1972,9 @@ func (m *SparseBuckets) Size() (n int) {
 		}
 		n += 1 + sovMetrics(uint64(l)) + l
 	}
+	if len(m.Count) > 0 {
+		n += 1 + sovMetrics(uint64(len(m.Count)*8)) + len(m.Count)*8
+	}
 	if m.XXX_unrecognized != nil {
 		n += len(m.XXX_unrecognized)
 	}
@@ -2747,6 +2841,28 @@ func (m *Histogram) Unmarshal(dAtA []byte) error {
 				return err
 			}
 			iNdEx = postIndex
+		case 9:
+			if wireType != 1 {
+				return fmt.Errorf("proto: wrong wireType = %d for field SampleCountFloat", wireType)
+			}
+			var v uint64
+			if (iNdEx + 8) > l {
+				return io.ErrUnexpectedEOF
+			}
+			v = uint64(encoding_binary.LittleEndian.Uint64(dAtA[iNdEx:]))
+			iNdEx += 8
+			m.SampleCountFloat = float64(math.Float64frombits(v))
+		case 10:
+			if wireType != 1 {
+				return fmt.Errorf("proto: wrong wireType = %d for field SbZeroCountFloat", wireType)
+			}
+			var v uint64
+			if (iNdEx + 8) > l {
+				return io.ErrUnexpectedEOF
+			}
+			v = uint64(encoding_binary.LittleEndian.Uint64(dAtA[iNdEx:]))
+			iNdEx += 8
+			m.SbZeroCountFloat = float64(math.Float64frombits(v))
 		default:
 			iNdEx = preIndex
 			skippy, err := skipMetrics(dAtA[iNdEx:])
@@ -2864,6 +2980,17 @@ func (m *Bucket) Unmarshal(dAtA []byte) error {
 				return err
 			}
 			iNdEx = postIndex
+		case 4:
+			if wireType != 1 {
+				return fmt.Errorf("proto: wrong wireType = %d for field CumulativeCountFloat", wireType)
+			}
+			var v uint64
+			if (iNdEx + 8) > l {
+				return io.ErrUnexpectedEOF
+			}
+			v = uint64(encoding_binary.LittleEndian.Uint64(dAtA[iNdEx:]))
+			iNdEx += 8
+			m.CumulativeCountFloat = float64(math.Float64frombits(v))
 		default:
 			iNdEx = preIndex
 			skippy, err := skipMetrics(dAtA[iNdEx:])
@@ -3027,6 +3154,60 @@ func (m *SparseBuckets) Unmarshal(dAtA []byte) error {
 			} else {
 				return fmt.Errorf("proto: wrong wireType = %d for field Delta", wireType)
 			}
+		case 3:
+			if wireType == 1 {
+				var v uint64
+				if (iNdEx + 8) > l {
+					return io.ErrUnexpectedEOF
+				}
+				v = uint64(encoding_binary.LittleEndian.Uint64(dAtA[iNdEx:]))
+				iNdEx += 8
+				v2 := float64(math.Float64frombits(v))
+				m.Count = append(m.Count, v2)
+			} else if wireType == 2 {
+				var packedLen int
+				for shift := uint(0); ; shift += 7 {
+					if shift >= 64 {
+						return ErrIntOverflowMetrics
+					}
+					if iNdEx >= l {
+						return io.ErrUnexpectedEOF
+					}
+					b := dAtA[iNdEx]
+					iNdEx++
+					packedLen |= int(b&0x7F) << shift
+					if b < 0x80 {
+						break
+					}
+				}
+				if packedLen < 0 {
+					return ErrInvalidLengthMetrics
+				}
+				postIndex := iNdEx + packedLen
+				if postIndex < 0 {
+					return ErrInvalidLengthMetrics
+				}
+				if postIndex > l {
+					return io.ErrUnexpectedEOF
+				}
+				var elementCount int
+				elementCount = packedLen / 8
+				if elementCount != 0 && len(m.Count) == 0 {
+					m.Count = make([]float64, 0, elementCount)
+				}
+				for iNdEx < postIndex {
+					var v uint64
+					if (iNdEx + 8) > l {
+						return io.ErrUnexpectedEOF
+					}
+					v = uint64(encoding_binary.LittleEndian.Uint64(dAtA[iNdEx:]))
+					iNdEx += 8
+					v2 := float64(math.Float64frombits(v))
+					m.Count = append(m.Count, v2)
+				}
+			} else {
+				return fmt.Errorf("proto: wrong wireType = %d for field Count", wireType)
+			}
 		default:
 			iNdEx = preIndex
 			skippy, err := skipMetrics(dAtA[iNdEx:])
diff --git a/prompb/io/prometheus/client/metrics.proto b/prompb/io/prometheus/client/metrics.proto
index 694c2c180..f0a0f40c4 100644
--- a/prompb/io/prometheus/client/metrics.proto
+++ b/prompb/io/prometheus/client/metrics.proto
@@ -29,11 +29,18 @@ message LabelPair {
 }
 
 enum MetricType {
-  COUNTER    = 0;
-  GAUGE      = 1;
-  SUMMARY    = 2;
-  UNTYPED    = 3;
-  HISTOGRAM  = 4;
+  // COUNTER must use the Metric field "counter".
+  COUNTER = 0;
+  // GAUGE must use the Metric field "gauge".
+  GAUGE = 1;
+  // SUMMARY must use the Metric field "summary".
+  SUMMARY = 2;
+  // UNTYPED must use the Metric field "untyped".
+  UNTYPED = 3;
+  // HISTOGRAM must use the Metric field "histogram".
+  HISTOGRAM = 4;
+  // GAUGE_HISTOGRAM must use the Metric field "histogram".
+  GAUGE_HISTOGRAM = 5;
 }
 
 message Gauge {
@@ -62,6 +69,7 @@ message Untyped {
 
 message Histogram {
   uint64 sample_count = 1;
+  double sample_count_float = 9; // Overrides sample_count if > 0.
   double sample_sum   = 2;
   repeated Bucket bucket       = 3; // Ordered in increasing order of upper_bound, +Inf bucket is optional.
   // Sparse bucket (sb) stuff:
@@ -70,26 +78,37 @@ message Histogram {
   // then each power of two is divided into 2^n logarithmic buckets.
   // Or in other words, each bucket boundary is the previous boundary times 2^(2^-n).
   // In the future, more bucket schemas may be added using numbers < -4 or > 8.
-  sint32 sb_schema          = 4;
-  double sb_zero_threshold  = 5; // Breadth of the zero bucket.
-  uint64 sb_zero_count      = 6; // Count in zero bucket.
-  SparseBuckets sb_negative = 7; // Negative sparse buckets.
-  SparseBuckets sb_positive = 8; // Positive sparse buckets.
+  sint32 sb_schema           = 4;
+  double sb_zero_threshold   = 5;  // Breadth of the zero bucket.
+  uint64 sb_zero_count       = 6;  // Count in zero bucket.
+  double sb_zero_count_float = 10; // Overrides sb_zero_count if > 0.
+  SparseBuckets sb_negative  = 7;  // Negative sparse buckets.
+  SparseBuckets sb_positive  = 8;  // Positive sparse buckets.
 }
 
 message Bucket {
-  uint64   cumulative_count = 1; // Cumulative in increasing order.
-  double   upper_bound      = 2; // Inclusive.
-  Exemplar exemplar         = 3;
+  uint64   cumulative_count       = 1; // Cumulative in increasing order.
+  double   cumulative_count_float = 4; // Overrides cumulative_count if > 0.
+  double   upper_bound            = 2; // Inclusive.
+  Exemplar exemplar               = 3;
 }
 
 message SparseBuckets {
+  // A Span is a given number of consecutive buckets at a given
+  // offset. Logically, it would be more straightforward to include
+  // the bucket counts in the Span. However, the protobuf
+  // representation is more compact in the way the data is structured
+  // here (with all the buckets in a single array separate from the
+  // Spans).
   message Span {
     sint32 offset = 1; // Gap to previous span, or starting point for 1st span (which can be negative).
     uint32 length = 2; // Length of consecutive buckets.
   }
-  repeated Span span    = 1;
+  repeated Span span = 1;
+  // Only one of "delta" or "count" may be used, the former for regular
+  // histograms with integer counts, the latter for float histograms.
   repeated sint64 delta = 2; // Count delta of each bucket compared to previous one (or to zero for 1st bucket).
+  repeated double count = 3; // Absolute count of each bucket.
 }
 
 message Exemplar {
@@ -99,18 +118,18 @@ message Exemplar {
 }
 
 message Metric {
-  repeated LabelPair label        = 1;
-  Gauge     gauge        = 2;
-  Counter   counter      = 3;
-  Summary   summary      = 4;
-  Untyped   untyped      = 5;
-  Histogram histogram    = 7;
-  int64     timestamp_ms = 6;
+  repeated LabelPair label = 1;
+  Gauge     gauge          = 2;
+  Counter   counter        = 3;
+  Summary   summary        = 4;
+  Untyped   untyped        = 5;
+  Histogram histogram      = 7;
+  int64     timestamp_ms   = 6;
 }
 
 message MetricFamily {
-  string     name   = 1;
-  string     help   = 2;
-  MetricType type   = 3;
-  repeated Metric     metric = 4;
+  string          name   = 1;
+  string          help   = 2;
+  MetricType      type   = 3;
+  repeated Metric metric = 4;
 }