NICHOLAS KAMM via Getty Images In an open letter published on RollingStone.com, the Grammy Award winner urged Obama to put an end to criminal injustice.

Before President Obama leaves office next month, John Legend has one last request for the commander-in-chief: “bring an end to the injustice that remains in our federal sentencing schemes.”

In an open letter published on RollingStone.com Friday, the Grammy Award winner urged Obama to grant clemency to federal inmates. In addition to commending the Obama administration’s progressive steps to end juvenile solitary confinement and reduce the use of federal private prisons, Legend expressed his concern for what’s at stake in the future for the country’s criminal justice system.

“While we hope the Trump administration and the 115th Congress will maintain this progress and continue to work in a bipartisan manner to reform our criminal justice system, it is unclear what their priorities will be and when families can expect justice,” he wrote.

“Before you leave office, I would like to add my voice to the more than 2 million Americans who have asked you to use your clemency and pardon powers to bring justice to the thousands of families of non-violent drug offenders who have waited far too long for Congress to act,” he added.

Over the course of his presidency, Obama has granted commutations to more than 1,000 federal inmates ― the most provided by a single president since Lyndon Johnson provided clemency to 1,187 inmates, according to Pew Research Center.

Legend implored Obama to grant the release of the more than 36,000 nonviolent federal drug offenders who, he wrote, are serving sentences based on “prejudiced laws” involving crack cocaine.

“I urge you to consider issuing categorical commutations to bring an end to the injustice that remains in our federal sentencing schemes... Rectifying these crack-powder disparities would not only correct the mistakes of the past, but could save taxpayers just over $150 million per year and keep with public sentiment about the over-incarceration and criminalization of drug crimes,” he wrote.

Legend has agitated for inmates in the past. This summer, he launched a digital storytelling initiative, My Potential, which features stories from family members who have personally been affected by incarceration, as well the personal experiences from those who are currently in prison and juvenile detention centers.

Read more of John Legend’s open letter to President Obama here.