Google fonts not loading properly over https

Hi I keep getting this error with google chrome when loading over https:

Mixed Content: The page at 'https://my-website' was loaded over HTTPS, but requested an insecure stylesheet ' fonts.googleapis.com/css?family=Oswald '. This request has been blocked; the content must be served over HTTPS.

I can't find where the template files are referencing this over http?

I found this in one of the files but it looks OK
$document->addScript($protocol.'/ajax.googleapis.com/ajax/libs/webfont/1/webfont.js');

But I can't find out where to fix this, please could you help?

Thanks

Here is the error in IE

SEC7111: HTTPS security is compromised by fonts.googleapis.com/css?family=Oswald