Variable replacement in Description not working

WordPress version: 3.4.2
WordPress SEO version: 1.2.8.7

I did this:
I’ve put in the Description field of a post the variable %%currentyear%%

I expected the plugin to do this:
By default, the plugin should replace the %%currentyear%% with the current year, in our case 2012.

Instead it did this:
If I look at the sourcecode of the page, the variable is shown in the description and not a replaces value.

The replacement works for titles, but not for descriptions.

Any idea which way to go, so that the %%currentyear%% is also replaced in the descriptions?

http://ww.wp.xz.cn/extend/plugins/wordpress-seo/