diff --git a/cmd/kubeadm/app/cmd/phases/kubelet.go b/cmd/kubeadm/app/cmd/phases/kubelet.go
index 91c87dd855c..068a6d2783c 100644
--- a/cmd/kubeadm/app/cmd/phases/kubelet.go
+++ b/cmd/kubeadm/app/cmd/phases/kubelet.go
@@ -125,6 +125,10 @@ func NewCmdKubeletWriteEnvFile() *cobra.Command {
 		Long:    kubeletWriteEnvFileLongDesc,
 		Example: kubeletWriteEnvFileExample,
 		Run: func(cmd *cobra.Command, args []string) {
+			if len(cfgPath) == 0 {
+				kubeadmutil.CheckErr(fmt.Errorf("The --config flag is mandatory"))
+			}
+
 			err := RunKubeletWriteEnvFile(cfgPath)
 			kubeadmutil.CheckErr(err)
 		},