Problem with Twitter cards

Hi,

I added Twitter cards to my website and I have some problems testing the card validator on https://cards-dev.twitter.com/validator !

I got this message for most of my pages
INFO: Page fetched successfully
INFO: 23 metatags were found
INFO: twitter:card = summary_large_image tag found
ERROR: Invalid value (message: Field description failed to validate because: text expects tag property, but not found in Map().)

Any idea how to fix that ?

Regards,
Janus