He's in favor of Glass-Steagall. Just not that Glass-Steagall.

Treasury Secretary Steven Mnuchin was lambasted Thursday by Sen. Elizabeth Warren for saying that he supported a "21st-century Glass-Steagall" Act, but opposed breaking up banks' commercial and investment banking functions.

"This is bizarre!" fumed Warren, a Massachusetts Democrat, at Mnuchin during a hearing on Capitol Hill that quickly turned contentious when it was her turn to question the Treasury chief.

"Tell me what 21st-century Glass-Steagall means if it doesn't mean breaking apart banks?" asked Warren. She noted, repeatedly, that the original Glass-Steagall Act passed into law in 1933 and repealed in 1999 broke commercial banks apart from investment banks.

Mnuchin tried to dodge Warren on that issue, saying, "It is a complicated question."

"I'll bet," Warren snapped.