Did not update TD1. Am I in big trouble?

I'm a foreign worker in Canada. I filled out TD1 when I started to work 2 years ago, and did put a full amount in "7. Spouse amount", because my spouse did not work at that time. Now I'm doing tax return for last year, and just realized that my spouse worked couple months last year without updating TD1. On CRA website it says, "Employees who do not fill out new forms may be penalized $25 for each day the form is late up to $2500".

I did not know about update obligation. I haven't filed last year's tax return yet. Is it too late to change? Am I going to pay $2500 penalty? What should I do?