Autofilling a textbox falsely triggers regular expression validator

My form has an email address textbox with a regular expression validor.  Everything works fine except for one occaision...
When the user selects the predictive text / cache for the textbox it automatically displays the validator message.  However, the validator is not actually tripped and the user can still submit the form.
Has anyone else run into this problem?  What's the best solution?

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