TypeError: output[i].author is not a function

I seem to be getting this error on repos I cloned a while ago. Cloning the same repo fresh resolves the issue...

``` sh
/Users/alan/Code/fun/git-days/node_modules/git-log/node_modules/git-walk-refs/index.js:77
_human = output[i].human = human(output[i].author() || output[i].commi
^
TypeError: output[i].author is not a function
at done (/Users/alan/Code/fun/git-days/node_modules/git-log/node_modules/git-walk-refs/index.js:77:52)
at /Users/alan/Code/fun/git-days/node_modules/git-log/node_modules/git-walk-refs/index.js:52:25
at /Users/alan/Code/fun/git-days/node_modules/git-log/node_modules/git-fs-repo/index.js:64:5
at got (/Users/alan/Code/fun/git-days/node_modules/git-log/node_modules/git-fs-repo/node_modules/git-odb/index.js:62:14)
at Stream. (/Users/alan/Code/fun/git-days/node_modules/git-log/node_modules/git-fs-repo/node_modules/git-odb-loose/index.js:40:35)
at emitOne (events.js:77:13)
at Stream.emit (events.js:169:7)
at drain (/Users/alan/Code/fun/git-days/node_modules/git-log/node_modules/git-fs-repo/node_modules/through/index.js:35:16)
at Stream.stream.queue.stream.push (/Users/alan/Code/fun/git-days/node_modules/git-log/node_modules/git-fs-repo/node_modules/through/index.js:41:5)
at done (/Users/alan/Code/fun/git-days/node_modules/git-log/node_modules/git-fs-repo/node_modules/git-odb-loose/parse.js:40:12)
```