Question [Q] Backup sd-ext (ext4) in cwm - is there any chance for that?

I have an xperia V LT25i with firmware .140 (JB 4.1.2) rooted with cwm v8.0 installed. I installed Link2sd app, moved a lot of apps on sd-ext, all is working fine. Then I wanted to do a cwm backup. But during that appeared a message like : "no sd-ext found: skipping backup...". I have a sd-ext partition formatted ext4, and after moving apps to sd-ext using link2sd everything is working perfect, as I mentioned before. I guess it's a bug in cwm. Is there any chance to fix that? Thanks in advance for an answer.