Stop link field requiring the "http://"

Registered users of my site have a link field on their profile so they can provide a link to their own websites.

When filling in this field the http:// is required, so wont work but will. This seems like terrible UX to be and will no doubt confuse less technical users.

Is there a way to stop the http:// being required? I could use a plain text field but then I lose all validation.

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