diff --git a/bootstrap/kubeadm/internal/webhooks/kubeadmconfig.go b/bootstrap/kubeadm/internal/webhooks/kubeadmconfig.go
index fbd0655dd26c..7a7c24936f48 100644
--- a/bootstrap/kubeadm/internal/webhooks/kubeadmconfig.go
+++ b/bootstrap/kubeadm/internal/webhooks/kubeadmconfig.go
@@ -33,7 +33,7 @@ import (
 func (webhook *KubeadmConfig) SetupWebhookWithManager(mgr ctrl.Manager) error {
 	return ctrl.NewWebhookManagedBy(mgr).
 		For(&bootstrapv1.KubeadmConfig{}).
-		WithDefaulter(webhook).
+		WithDefaulter(webhook, admission.DefaulterRemoveUnknownOrOmitableFields).
 		WithValidator(webhook).
 		Complete()
 }
diff --git a/bootstrap/kubeadm/internal/webhooks/kubeadmconfigtemplate.go b/bootstrap/kubeadm/internal/webhooks/kubeadmconfigtemplate.go
index 5f9efa867ca9..70212813645b 100644
--- a/bootstrap/kubeadm/internal/webhooks/kubeadmconfigtemplate.go
+++ b/bootstrap/kubeadm/internal/webhooks/kubeadmconfigtemplate.go
@@ -32,7 +32,7 @@ import (
 func (webhook *KubeadmConfigTemplate) SetupWebhookWithManager(mgr ctrl.Manager) error {
 	return ctrl.NewWebhookManagedBy(mgr).
 		For(&bootstrapv1.KubeadmConfigTemplate{}).
-		WithDefaulter(webhook).
+		WithDefaulter(webhook, admission.DefaulterRemoveUnknownOrOmitableFields).
 		WithValidator(webhook).
 		Complete()
 }
diff --git a/controlplane/kubeadm/internal/webhooks/kubeadm_control_plane.go b/controlplane/kubeadm/internal/webhooks/kubeadm_control_plane.go
index 8a8b7cb10c0a..bd5a21fb4293 100644
--- a/controlplane/kubeadm/internal/webhooks/kubeadm_control_plane.go
+++ b/controlplane/kubeadm/internal/webhooks/kubeadm_control_plane.go
@@ -47,7 +47,7 @@ import (
 func (webhook *KubeadmControlPlane) SetupWebhookWithManager(mgr ctrl.Manager) error {
 	return ctrl.NewWebhookManagedBy(mgr).
 		For(&controlplanev1.KubeadmControlPlane{}).
-		WithDefaulter(webhook).
+		WithDefaulter(webhook, admission.DefaulterRemoveUnknownOrOmitableFields).
 		WithValidator(webhook).
 		Complete()
 }
diff --git a/controlplane/kubeadm/internal/webhooks/kubeadmcontrolplanetemplate.go b/controlplane/kubeadm/internal/webhooks/kubeadmcontrolplanetemplate.go
index aa52aeffb25f..6251f7d814d8 100644
--- a/controlplane/kubeadm/internal/webhooks/kubeadmcontrolplanetemplate.go
+++ b/controlplane/kubeadm/internal/webhooks/kubeadmcontrolplanetemplate.go
@@ -36,7 +36,7 @@ import (
 func (webhook *KubeadmControlPlaneTemplate) SetupWebhookWithManager(mgr ctrl.Manager) error {
 	return ctrl.NewWebhookManagedBy(mgr).
 		For(&controlplanev1.KubeadmControlPlaneTemplate{}).
-		WithDefaulter(webhook).
+		WithDefaulter(webhook, admission.DefaulterRemoveUnknownOrOmitableFields).
 		WithValidator(webhook).
 		Complete()
 }