Multiline prompt stopped working on macOS

[certik]

I get the following on macOS M1:

$ ./prompt_multiline
Interactive prompt.
  * Use Ctrl-D to exit.
  * Use Enter to submit.
  * Features:
    - Editing (Keys: Left, Right, Home, End, Backspace)
    - History (Keys: Up, Down)
    - Multi-line editing (use CTRL+N to add a new line)

it never shows the prompt. This used to work.