Fatal error while creating a form

Hi there,
I tried to create a new form and after clicking on save form I’ve got the following message: Fatal error: Call to undefined function wp_verify_nonce() in /public/sites/www.therapy.brussels/wp-content/plugins/lead-form-builder/inc/create-lead-form.php on line 5

And of course I can’t create the form because of that.
Is this a bug in the plugin? or am I doing something wrong…?

Thanks in advance.