TYPO3 Core

When I do:
t3lib_SpriteManager::addTcaTypeIcon('pages', 'contains-myext', '../typo3conf/myext/res/icons/calendar.gif');
$TCA['pages']['columns']['module']['config']['items']⁶⁰ = 'Kalender';
$TCA['pages']['columns']['module']['config']['items']⁶¹ = 'calendar';
$TCA['pages']['columns']['module']['config']['items']⁶² = t3lib_extMgm::extRelPath($_EXTKEY) . 'res/icons/calendar.gif';

It is well loaded in the listview and in the pageproperty-frame etc.

The icon is NOT loaded in the pagetree.
The icon-span has the correct class:
<span class="t3-icon t3-icon-tcarecords t3-icon-tcarecords-pages t3-icon-pages-contains-calendar" id="ext-gen1075" qtip="id=127"> </span>

in the merged css-file is:
.t3-icon-pages-contains-calendar{background-position:0px 0px !important;background-image:url('../../typo3conf/ext/klicksafe/res/icons/calendar.gif') !important}

which is one '../' to much