Can't mark snap as viewed

[Suppen]

When I try to mark a snap as viewed with client.snaps.markSnapViewed(), it gives me the following error and stack trace:

TypeError: Cannot read property 'addedFriendsTimestamp' of undefined
    at Snaps.markSnapsViewed (./node_modules/snapchat/routes/snaps.js:121:70)
    at Snaps.markSnapViewed (./node_modules/snapchat/routes/snaps.js:92:15)
    ....

I have barely ever used Snapchat, but I can't see a reason why marking a snap as viewed would require any such timestamp. Is it supposed to be there?