Adjacent shortcodes don’t get parsed in WP 2.8

Say I have the shortcode [span]text[/span] that expands to <span>text<span>. If I write [span]one[/span][span]two[/span] without any spaces between the two shortcodes, I get:

<span>one<span>[span]two[/span]

Before upgrading to WordPress 2.8, they both used to get parsed correctly into:

<span>one<span><span>two<span>

If I add a space between them ([span]one[/span] [span]two[/span]) then I get the correct result – however, I’d rather not have to update tens of old posts to reflect this new behaviour.

Any ideas? Thanks!