diff --git a/pkg/util/webhook/webhook.go b/pkg/util/webhook/webhook.go
index b03640ae8..8552e91eb 100644
--- a/pkg/util/webhook/webhook.go
+++ b/pkg/util/webhook/webhook.go
@@ -83,6 +83,7 @@ func NewGenericWebhook(scheme *runtime.Scheme, codecFactory serializer.CodecFact
 	clientConfig := rest.CopyConfig(config)
 
 	codec := codecFactory.LegacyCodec(groupVersions...)
+	clientConfig.ContentType = runtime.ContentTypeJSON
 	clientConfig.ContentConfig.NegotiatedSerializer = serializer.NegotiatedSerializerWrapper(runtime.SerializerInfo{Serializer: codec})
 
 	clientConfig.Wrap(x509metrics.NewDeprecatedCertificateRoundTripperWrapperConstructor(
diff --git a/pkg/util/webhook/webhook_test.go b/pkg/util/webhook/webhook_test.go
index 068c6821e..dba0e3ed6 100644
--- a/pkg/util/webhook/webhook_test.go
+++ b/pkg/util/webhook/webhook_test.go
@@ -23,6 +23,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"io"
 	"net"
 	"net/http"
 	"net/http/httptest"
@@ -33,11 +34,15 @@ import (
 	"strings"
 	"testing"
 	"time"
+	"unicode/utf8"
 
 	apierrors "k8s.io/apimachinery/pkg/api/errors"
 	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/runtime/schema"
+	"k8s.io/apimachinery/pkg/runtime/serializer"
 	"k8s.io/apimachinery/pkg/util/wait"
+	exampleinstall "k8s.io/apiserver/pkg/apis/example/install"
+	examplev1 "k8s.io/apiserver/pkg/apis/example/v1"
 	"k8s.io/client-go/kubernetes/scheme"
 	"k8s.io/client-go/rest"
 	v1 "k8s.io/client-go/tools/clientcmd/api/v1"
@@ -927,3 +932,57 @@ func getSingleCounterValueFromRegistry(t *testing.T, r metrics.Gatherer, name st
 
 	return -1
 }
+
+func TestRESTConfigContentType(t *testing.T) {
+	server, err := newTestServer(clientCert, clientKey, caCert, func(w http.ResponseWriter, r *http.Request) {
+		if got := r.Header.Get("Content-Type"); got != runtime.ContentTypeJSON {
+			t.Errorf("expected request content-type: want %q got %q", runtime.ContentTypeJSON, got)
+		}
+		body, err := io.ReadAll(r.Body)
+		if err != nil {
+			t.Errorf("failed to read request body: %v", err)
+			return
+		}
+		if err := json.Unmarshal(body, new(any)); err != nil {
+			switch {
+			case len(body) == 0:
+				t.Log("empty request body")
+			case utf8.Valid(body):
+				t.Logf("request body: %s", string(body))
+			default:
+				t.Logf("request body: 0x%x", body)
+			}
+			t.Errorf("failed to unmarshal request body as json: %v", err)
+		}
+	})
+	if err != nil {
+		t.Errorf("failed to create server: %v", err)
+		return
+	}
+	defer server.Close()
+
+	config := &rest.Config{
+		ContentConfig: rest.ContentConfig{
+			ContentType: "foo/bar",
+		},
+		Host: server.URL,
+		TLSClientConfig: rest.TLSClientConfig{
+			CAData:   caCert,
+			CertData: clientCert,
+			KeyData:  clientKey,
+		},
+	}
+
+	scheme := runtime.NewScheme()
+	exampleinstall.Install(scheme)
+	codecs := serializer.NewCodecFactory(scheme)
+	groupVersions := []schema.GroupVersion{examplev1.SchemeGroupVersion}
+	wh, err := NewGenericWebhook(scheme, codecs, config, groupVersions, retryBackoff)
+	if err != nil {
+		t.Fatalf("failed to create the webhook: %v", err)
+	}
+
+	if err := wh.RestClient.Post().Body(&examplev1.Pod{}).Do(context.TODO()).Error(); err != nil {
+		t.Fatalf("failed to complete request: %v", err)
+	}
+}