diff --git a/pkg/util/configz/configz.go b/pkg/util/configz/configz.go
index cc2aa3a9fe..99413d5e7f 100644
--- a/pkg/util/configz/configz.go
+++ b/pkg/util/configz/configz.go
@@ -19,7 +19,6 @@ package configz
 import (
 	"encoding/json"
 	"fmt"
-	"io"
 	"net/http"
 	"sync"
 )
@@ -74,7 +73,7 @@ func handle(w http.ResponseWriter, r *http.Request) {
 	}
 }
 
-func write(w io.Writer) error {
+func write(w http.ResponseWriter) error {
 	var b []byte
 	var err error
 	func() {
@@ -85,6 +84,7 @@ func write(w io.Writer) error {
 	if err != nil {
 		return fmt.Errorf("error marshaling json: %v", err)
 	}
+	w.Header().Set("Content-Type", "application/json")
 	_, err = w.Write(b)
 	return err
 }
diff --git a/pkg/util/configz/configz_test.go b/pkg/util/configz/configz_test.go
index 78f22593d1..850739df2e 100644
--- a/pkg/util/configz/configz_test.go
+++ b/pkg/util/configz/configz_test.go
@@ -44,7 +44,7 @@ func TestConfigz(t *testing.T) {
 		t.Fatalf("err: %v", err)
 	}
 	if string(body) != `{"testing":"blah"}` {
-		t.Fatalf("unexpected output: %v", err)
+		t.Fatalf("unexpected output: %s", body)
 	}
 
 	v.Set("bing")
@@ -58,7 +58,7 @@ func TestConfigz(t *testing.T) {
 		t.Fatalf("err: %v", err)
 	}
 	if string(body) != `{"testing":"bing"}` {
-		t.Fatalf("unexpected output: %v", err)
+		t.Fatalf("unexpected output: %s", body)
 	}
 
 	Delete("testing")
@@ -72,6 +72,9 @@ func TestConfigz(t *testing.T) {
 		t.Fatalf("err: %v", err)
 	}
 	if string(body) != `{}` {
-		t.Fatalf("unexpected output: %v", err)
+		t.Fatalf("unexpected output: %s", body)
+	}
+	if resp.Header.Get("Content-Type") != "application/json" {
+		t.Fatalf("unexpected Content-Type: %s", resp.Header.Get("Content-Type"))
 	}
 }