Former Fed Chairman Ben Bernanke said he is "appalled" by the treasury secretary's decision to have Alexander Hamilton split his duty as the face of the $10 bill with a woman.
Though he said secretary Jack Lew's decision to put a female face on the ten is a "fine idea," Bernanke made it clear he doesn't think it should be at Hamilton's expense.
"Hamilton, the first Secretary of the Treasury, would qualify as among the greatest of our founders for his contributions to achieving American independence and creating the Constitution alone," Bernanke wrote in a blog post.
Bernanke argued that Hamilton also helped stabilize and strengthen the U.S. financial system in the early days of America, paving the way for a strong economy.
Related: It's time to put a woman on the $20 bill
"The importance of Hamilton's achievement can be judged by the problems that the combination of uncoordinated national fiscal policies and a single currency has caused the Eurozone in recent years," he wrote, adding that Hamilton's efforts to consolidate state debts and to create a strong federal fiscal system helped America avoid some of the eurozone's current issues.
Bernanke added that he supports Lew's historic decision to put a woman on U.S. paper currency for the first time in more than a century.
"As many have pointed out, a better solution is available: Replace Andrew Jackson, a man of many unattractive qualities and a poor president, on the twenty dollar bill," he said.
Lew said the U.S. Treasury selected the ten for a redesign because it's the next bill in line to have its security features updated. The current version of the $10 bill has been in circulation since 2006, however, while the $20 bill has not been updated since 2003, according to the U.S. Bureau of Engraving and Printing.
It remains unclear whether Hamilton will appear alongside a woman on the new $10 bill or be the centerpiece of one version of the new bill. Lew said the details are still up for discussion.
Related: The right woman for the $10 bill
Either way, the Hamilton $10 isn't going anywhere soon, since there are about 1.9 billion $10s in circulation today.
Advocacy groups have helped promote a national movement to put a woman on U.S. currency that was then backed by members of Congress.
That campaign, spearheaded by the group Women on 20's, also called for replacing Andrew Jackson.
Bernanke previously shared his criticism of Lew's decision with the media, but his blog post Monday morning marks the first time he has written on the subject.
