Californias Senate passed a bill Thursday banning menstrual products from being taxed, marking a major step toward ending whats known as the tampon tax.

The same bill unanimously passed in the Assembly in early June. It now heads back to the Assembly for final approval, and then to Gov. Jerry Brown (D), whose office declined to say if he will sign the bill into law or not. The measure would save California women an estimated $20 million annually, and has the support of the states tax board .

California is one of 39 states where tampons, pads and other similar items are not classified as necessities and are thus subject to sales tax, unlike many other medical products .

The legislation, introduced by state Assemblywomen Cristina Garcia (D) and Ling Ling Chang (R) earlier this year, would exempt menstrual products from the state sales tax. The bills proponents argue that items like tampons are not simply feminine hygiene products, but a medical necessity for women, and that subjecting the products to sales tax is a glaring example of gender inequality.

The state of California should not be in the business of putting a tax on half the population because they were born as women, Garcia told The Huffington Post in April.