Skype repository key expired?

When I apt-get update, the repository for Microsoft's Skype says:

W: An error occurred during the signature verification. 
The repository is not updated and the previous index files will be used.
GPG error: https://repo.skype.com/deb  stable InRelease: The following signatures were invalid:
EXPKEYSIG 1F3045A5DF7587C3 Skype Linux Client Repository 
W: Failed to fetch https://repo.skype.com/deb/dists/stable/InRelease    
The following signatures were invalid: 
EXPKEYSIG 1F3045A5DF7587C3 Skype Linux Client Repository 
W: Some index files failed to download. They have been ignored, or old ones used instead.

Why is this happening? Is there something wrong with my system? And what should I do?