"Cannot open load file: No such file or directory, json-mode"

[8573]

I get this error message

Error (use-package): nix-mode/:catch: Cannot open load file: No such file or directory, json-mode

from this simple use-package stanza:

(use-package
  nix-mode
  :pin nongnu)

With this error, nix-mode does not seem to work, that is, it does not activate on Nix files that I visit. I installed nix-mode from NonGNU ELPA through M-x package-list-packages and I think it previously worked as expected within the last few months. I don't know what might have changed to make it stop working.

I see that some other issue reports have been filed about undeclared dependencies on json-mode, but I see that those issues were thought to be fixed.

In case more information is needed, I note that I may be slow to respond.