The proposed amendment to Italy's Civil Code would remove the word "fidelity" from Italian marriage contracts.
The promise not to cheat is a "cultural legacy from an outdated and obsolete vision of marriage, family, and the rights and duties of spouses", according to the senators who have signed the bill.
They cited a previous ruling from Italy's top court, which declared that judges could not legally place the blame for a marriage separation "on the mere failure to observe the duty of fidelity".
Instead, the other party has to prove that their spouse's infidelity led to the irreconcilable breakdown of the marriage.
The bill, which was presented to the Italian Senate last year and has now been passed to its Judiciary Committee, goes on to argue that there is an element of sexism in the current wording. It was originally included to refer to the woman's sexual fidelity, in order to determine whether children were "legitimate", they noted.
"Until not long ago, only the fidelity of the woman was sufficient to guarantee the 'legitimacy' of children," the bill notes, saying that since the "hateful" legal distinction between "legitimate" and "natural" children was scrapped in a 2012 ruling, there is no longer a need for the clause.
The senators assert that fidelity should not be thought of only in sexual terms, but also in terms of "trust and respect", and that while it was an "important value", it should not be up to the State to impose it by law.
References to fidelity and faithfulness were removed from Italy's civil unions bill which was passed earlier this year - a change which provoked outcry from some of the LGBT community, who saw this as a failure to acknowledge the parity of same-sex and opposite-sex romantic relationships.
Instead, that bill simply refers to "moral and material support" and "cohabitation".
Laura Cantini, one of the senators arguing for the fidelity clause to be dropped from heterosexual marriage, said that the wording of the civil unions bill is "a much more advanced model".
As to whether Italians live up to their reputation as Casanovas, the jury's still out.
A 2013 poll showed that 55 percent of men and one in three women in Italy admitted to cheating on their partners, making them the most likely to be unfaithful in Europe.
But that was only slightly higher than the Brits and the Germans, who scored 42 and 46 percent respectively, and it's possible that Italians are just more open about their affairs.
READ MORE: 'British men cheat more than Italians'