If the husband and wife had a joint account, the bank is likely to deposit the check as long as the wife presents a copy of the death certificate. Or if the wife is executor of the husband's estate and has documentation to this effect, the bank should honor her signature.
If neither of these things are true, however, or the bank still won't comply, you may wish to have the wife submit a written request to you to have the check reissued.
She would simply state that her husband is deceased and that she is the surviving spouse and entitled to receive the payment. Although this isn't really necessary, it gives you documentation should a question arise later.