The rapper was caught off guard when Fox came up in an interview.
Megan Fox and Machine Gun Kelly appear very comfortable with each other -- but that doesn't mean he's necessarily comfortable talking about her just yet.
The rapper was a guest on RADIO.COM's FANDEMIC Instagram Live on Thursday, where eventually talk turned to his music video for "Bloody Valentine," which also features his now-girlfriend.
"What was it like working with Megan Fox in the 'Bloody Valentine' music video?" asked the host, reading a viewer question. It starts around the 14:30 mark below.
He didn't immediately know how to answer, smiling and laughing while taking a beat to think about how to respond. "Good work experience?" asked the host. "Great work experience," he said with a laugh.
"I was playing Megan a lot of the Tickets to My Downfall songs," he explained.
"I don't know ... I had to ... I had made the call the day before the video and I was like, 'Can you come over?' and then we shot the video," he added.
Fox and the rapper were first spotted together in May, days before her now-estranged husband Brian Austin Green confirmed they had separated. In his statement, Green even brought up her relationship with MGK.
"I've never met him, but Megan and I have talked about him," he wrote. "They're friends at this point, and from what she's expressed, he's a really nice, genuine guy, and I trust her judgment."
After her appearance in the video and multiple PDA paparazzi photos, MGK appeared to confirm she was his girlfriend by tweeting out some lyrics from "Bloody Valentine."