vm-do-summary: Invalid function: (m-list m-list)

I downloaded the VM main branch (85359a60) and ran vm. The only line in ~/.vm is

(setq vm-primary-inbox "~/.Mail/inbox")

I immediately get messages:

inbox: Generating summary... 0
vm-do-summary: Invalid function: (m-list m-list)

and the inbox Summary buffer looks wrong. This error repeats each time I move to a new message by pressing "p" or "n".