California lawmakers on Thursday approved a measure intended to help female employees receive the equal pay to their male counterparts.

Pay differentials are allowed only if based on factors other than an employee’s sex, such as seniority, merit, experience or education.

The proposal, by state Sen. Hannah-Beth Jackson (D-Santa Barbara), would prohibit employers from retaliating or discriminating against employees who inquire about co-workers’ wages. It would also clarify the factors on which employers can make pay differentials: They would need to be job-related and consistent with business necessity.

Supporters of the measure said it would be the strongest equal pay law in the nation.