Drupal 7: Cron claims webform module function to be undefined I cant really figure this out.

I have a module which interacts with the webform module which just works perfectly fine.

But now I wanted to create a cron which updates certain submissions, but the cron function claims that suddenly the webform function webform_get_submission is undefined although all other mymodule functions use webform functions without any issues. How come?

// a whole lot functions which use webform functions
// [...]

function mymmodule_cron() {
    $conf = mymmodule_defaults();

    // check cron run
    if(true /* for testing */){

        // set writable User
        global $user;
        $original_user = $user;
        $old_state = drupal_save_session(FALSE);
        $user = user_load(1);

        // fancy sql statement
        $sql = array();
        // [...]
        $sql = join(" ",$sql);
        $result = db_query($sql);

        $queue = DrupalQueue::get('mymmodule_cron_archiveanon');

        foreach ($result as $row) {
            $row-&gt;anon = true;
            $queue-&gt;createItem($row);           
        }      

        // restore default user
        $user = $original_user;
        drupal_save_session($old_state); 
    }

}

function mymmodule_cron_archiveanon_wrapper($item){
    $node = node_load($item-&gt;nid);

    if( function_exists('webform_get_submission')) {
        die("Yep."); 
        // $submission = webform_get_submission($item-&gt;nid, $item-&gt;sid);
    }
    else {
        die("Nope.");
        // dies here
    }

    // custom function
    // mymmodule_contract_archive($node, $submission, $item-&gt;anon);

}
That function is in a file that isn't included by default; you just need to include it yourself:

module_load_include('inc', 'webform', 'includes/webform.submissions');