What I have to do to the image challenge never appears?

My authentication page is inside an iframe, for issues of usability. When the new google recaptcha appears in the images challenge, does not fit in the iframe and can not identify the size to resize the iframe. How to solve? -- You received this message because you are subscribed to the Google Groups "reCAPTCHA" group. To unsubscribe from this group and stop receiving emails from it, send an email to recaptcha+unsubscribe@googlegroups.com. To post to this group, send email to recaptcha@googlegroups.com. Visit this group at http://bit.ly/1dkFnYd. For more options, visit http://bit.ly/P65DvS.