The Burn singer has worked with her good pal on tracks I Need Your Love and Outside, and she revealed they had teamed up for another song when she sent a message into The Radio 1 Breakfast Show with Nick Grimshaw for the DJ's interview on Friday (29Apr16).
Ellie informed Nick that Calvin was being secretive about what was happening with their next collaboration, so Nick read out Ellie's message, saying, "Can you ask him when our next song is going to be ready, slash, out?"
Calvin reacted awkwardly to the question, insisting they hadn't even finished the track yet so Ellie needs to come back into his studio to work on it.
"I mean, that's insane," Calvin replied. "It's impossible to say, isn't it? She did record a vocal for me but there's no hook at the moment to that track... So it's kind of hard to say. I think she needs to get probably back in (the studio) in order to finish it... I can't just conjure up something."
He then joked that he could finish it by singing himself but he doesn't want to make a duet like Kylie Minogue and Jason Donovan's 1988 song Especially For You.
"It's hard to say Ellie, I'm sorry," he concluded. "But any queries feel free to text me direct, rather than do it live on Radio 1."
Ellie's question came after Calvin's fellow DJ Diplo and sister band Haim sent in queries to the show for Calvin to answer. Haim asked which band member he would like to go shopping with while Diplo wanted to know about Calvin's exercise equipment and why Rihanna wasn't texting him back.
"She won't text me back either," Calvin replied. "She's just chilling. I'm not sure if she's even got a phone sometimes... well that's fine, she's Rihanna. She's in the moment."