diff --git a/go/metrics.pb.go b/go/metrics.pb.go
index cee360d..dabae2c 100644
--- a/go/metrics.pb.go
+++ b/go/metrics.pb.go
@@ -923,6 +923,7 @@ type MetricFamily struct {
 	Help   *string     `protobuf:"bytes,2,opt,name=help" json:"help,omitempty"`
 	Type   *MetricType `protobuf:"varint,3,opt,name=type,enum=io.prometheus.client.MetricType" json:"type,omitempty"`
 	Metric []*Metric   `protobuf:"bytes,4,rep,name=metric" json:"metric,omitempty"`
+	Unit   *string     `protobuf:"bytes,5,opt,name=unit" json:"unit,omitempty"`
 }
 
 func (x *MetricFamily) Reset() {
@@ -985,6 +986,13 @@ func (x *MetricFamily) GetMetric() []*Metric {
 	return nil
 }
 
+func (x *MetricFamily) GetUnit() string {
+	if x != nil && x.Unit != nil {
+		return *x.Unit
+	}
+	return ""
+}
+
 var File_io_prometheus_client_metrics_proto protoreflect.FileDescriptor
 
 var file_io_prometheus_client_metrics_proto_rawDesc = []byte{
@@ -1121,7 +1129,7 @@ var file_io_prometheus_client_metrics_proto_rawDesc = []byte{
 	0x69, 0x73, 0x74, 0x6f, 0x67, 0x72, 0x61, 0x6d, 0x52, 0x09, 0x68, 0x69, 0x73, 0x74, 0x6f, 0x67,
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@@ -1131,19 +1139,20 @@ var file_io_prometheus_client_metrics_proto_rawDesc = []byte{
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 }
 
 var (
diff --git a/io/prometheus/client/metrics.proto b/io/prometheus/client/metrics.proto
index c3c8cc1..31595d8 100644
--- a/io/prometheus/client/metrics.proto
+++ b/io/prometheus/client/metrics.proto
@@ -150,4 +150,5 @@ message MetricFamily {
   optional string     help   = 2;
   optional MetricType type   = 3;
   repeated Metric     metric = 4;
+  optional string     unit   = 5;
 }