gistfile1.diff

diff --git a/prometheus/registry.go b/prometheus/registry.go
index ebe9871..32b4192 100644
--- a/prometheus/registry.go
+++ b/prometheus/registry.go
@@ -14,6 +14,7 @@ import (
   "fmt"
 	"io"
 	"log"
+	"mime"
 	"net/http"
 	"sort"
 	"strings"
@@ -241,7 +242,13 @@ func (registry registry) Handler() http.HandlerFunc {
 		if strings.HasSuffix(url.Path, jsonSuffix) {
 			header := w.Header()
 			header.Set(ProtocolVersionHeader, APIVersion)
-			header.Set(contentTypeHeader, jsonContentType)
+			header.Set(contentTypeHeader, mime.FormatMediaType(
+				"application/json",
+				map[string]string{
+					"schema":  "prometheus/telemetry",
+					"version": APIVersion,
+				},
+			))
 
 			writer := decorateWriter(r, w)