The proximity sensor doesn't seem to work on iPhone 13

Hello,
I have an iPhone 13, but when I'm on a phone call, voiceover speaks when a notification comes when the phone is close to my ears and I'm speaking through the speakerphone.
On my old iPhone se2, voiceover used to stop speaking when I got the phone close to my ear.
Is there any fix for this problem? It gets a bit annoying and destracting when I'm on a call.