The 'Someone You Loved' hitmaker and former One Direction star have become good friends and they've been using their time at home due to the coronavirus pandemic to catch up on video conferencing app Zoom while laying down some ideas for new songs.
In an Instagram Live, Niall said: ''I didn't see him this weekend.
''We usually have a few drinks on a Saturday night on Zoom but we didn't chat this weekend.
''I think I'm writing with him at some point this week. We have a little schedule going.''
The two musicians - who were set to hit the road together this year for the 'Nice To Meet Ya' tour before the health crisis meant the run had to be cancelled - have worked on new material together in the past.
Opening up on their secret collaboration, Lewis previously joked: ''We did do a song together. I love it.
''I don't know if it will come out, I hope it will. I really, really need the money.''
Meanwhile, the 23-year-old singer has also been writing his own songs to make the most of his time at home during lockdown.
The Scottish star has had no problem with writer's block, but insisted not everything he's churning out will be usable, as he quipped that ''diarrhoea also flows''.
He recently said: ''It's flowing, but diarrhoea also flows, doesn't mean that you want it!
''It's going pretty well so far but I'm just getting started, and everything I do right now I am like, 'Oh, that's exciting.'
''But when you everything goes back to normal, I'll realise I've written 12 songs about the same four walls.''
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