ReferenceError: Can't find variable: jQuery

Hi all,

this my jQuery fonction in the file customs.js :

jQuery(document).ready(function($) {
	var img = new Image();
	var images = ['header-box-bck-1.png', 'header-box-bck-2.png', 'header-box-bck-3.png', 'header-box-bck-4.png', 'header-box-bck-5.png', 'header-box-bck-6.png',];
    img.src = 'my_URL/' + images[Math.floor(Math.random() * images.length)] + '';

	$(img).one('load',function(e) {
		$('.background').html(img);
		$('.background img').fadeIn(3000);
	});

	if(img.complete) img.trigger('load');
 });

and I make an wp_enqueue_script of customs.js in my functions.php, I load correctly my script but I have this on my console : ReferenceError: Can’t find variable: jQuery.

Maybe an idea ?
tks for your help !