'required' error always triggered

I have been making a very basic form with the formproc module, but i keep on getting an error when i want a textfield to be required. When i fill in something in the textbox, i still get an error that the field should be filled in after submitting, even though it is.

Below is the form creation code:

function timetable_form_def(&$node) {

	// Initialize form.
	$form = array('NODE'=>&$node);
	$form['course'] = array(	
		'type'     => 'text',
		'name'     => 'course',
		'help'     => 'Course',
		'required' => true,
	);
	$form['format'] = array(
		'name' => 'format',
		'html' => filter_form('format', $node->format),
	);

	return $form;
}

What could cause this? I don't think i did anything special, as this is a very basic form...