Open in a new windows link in Request data form

I try to make a link to the current item in the edit task form and i want it to open in a new window.

I created a text variable in the workflow filled with a Build string action configurated with this text :
<a href="{Common:ContextItemUrl}"target="_blank">Item link</a>
and with option Parse for tokens twice checked

In Edit task form, I added a text label in which I inserted a link made with the above variable.

But it doesn't work : on the validation form, the label is correct but the link doesn't work (page error "sorry, something went wrong..."