I have implemented the jQuery UI autocomplete script, but the autocomplete is not firing on first character.

I have an input field with a static value on page load. When I change this value, the autocomplete is not firing. When I delete the character I typed and type it again, the autocomplete is working.

Am I doing something wrong? I can't find any information about this problem.

2. var quantities = ['10','20','25','30','35'];
3. $('#quantity').autocomplete({
4.         minChars:1,
5.         noCache: true,
6.         source: function( request, response ) {
7.             var matches = $.map( quantities, function(quantity) {
8.               if ( quantity.toUpperCase().indexOf(request.term.toUpperCase()) === 0 ) {
9.                 return quantity;
10.               }
11.             });
12.             response(matches);
13.         }
14.     });

I hope somebody can help me :)