diff --git a/cmd/kubeadm/app/apis/kubeadm/v1beta1/bootstraptokenstring.go b/cmd/kubeadm/app/apis/kubeadm/v1beta1/bootstraptokenstring.go
index 45817a8705f..97edd445407 100644
--- a/cmd/kubeadm/app/apis/kubeadm/v1beta1/bootstraptokenstring.go
+++ b/cmd/kubeadm/app/apis/kubeadm/v1beta1/bootstraptokenstring.go
@@ -31,8 +31,8 @@ import (
 // of view and as an authentication method for the node in the bootstrap phase of
 // "kubeadm join". This token is and should be short-lived
 type BootstrapTokenString struct {
-	ID     string
-	Secret string
+	ID     string `json:"-"`
+	Secret string `json:"-"`
 }
 
 // MarshalJSON implements the json.Marshaler interface.
diff --git a/cmd/kubeadm/app/apis/kubeadm/v1beta2/bootstraptokenstring.go b/cmd/kubeadm/app/apis/kubeadm/v1beta2/bootstraptokenstring.go
index f5a5b36ef24..2408f5e33b8 100644
--- a/cmd/kubeadm/app/apis/kubeadm/v1beta2/bootstraptokenstring.go
+++ b/cmd/kubeadm/app/apis/kubeadm/v1beta2/bootstraptokenstring.go
@@ -31,8 +31,8 @@ import (
 // of view and as an authentication method for the node in the bootstrap phase of
 // "kubeadm join". This token is and should be short-lived
 type BootstrapTokenString struct {
-	ID     string
-	Secret string
+	ID     string `json:"-"`
+	Secret string `json:"-"`
 }
 
 // MarshalJSON implements the json.Marshaler interface.