Sortable not working with hidden div's

Sortable not working with hidden div's

I also have a draggable list in the page.

When the page loads, the div containing the sortable is hidden through display: none and the draggable is disabled.

When the user clicks the link to show the sortable div, it displays using the show() function and the draggable is enabled. All this works as expected.

If the user then tries to move an element from the draggable list into the sortable list, nothing happens. The draggable works as expected, but the sortable refuses to accept any items.

But if I move an item already in the sortable list and then try to drop a draggable into the sortable list, it will work. It's like the sortable list has to be activated by moving one of its own items.