libcaphe outputs error message when running Goodvibes on XFCE

When running Goodvibes on XFCE, the following error message is shown:

[Caphe] Error while inhibiting: GDBus.Error:org.freedesktop.DBus.Error.UnknownMethod: Method "Inhibit" with signature "susu" on interface "org.xfce.SessionManager" doesn't exist

Could someone please explain why and what is wrong?

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