Trouble merging videos with VLC

I'm trying to merge three short videos (each under 10 seconds). Here is my command:

vlc 1.mp4 2.mp4 3.mp4 --sout "#gather:std{access=file,dst=final.mp4}" --sout-keep

which returns this

VLC media player 3.0.7 Vetinari (revision 3.0.7-0-g86cee31)
[0000000000d7b400] main libvlc: Running vlc with the default interface. Use 'cvlc' to use vlc without interface.
TagLib: MP4: No audio tracks
TagLib: MP4: No audio tracks
TagLib: MP4: No audio tracks
Qt: Session management error: None of the authentication protocols specified are supported
TagLib: MP4: No audio tracks
TagLib: MP4: No audio tracks
TagLib: MP4: No audio tracks
TagLib: MP4: No audio tracks
QObject::~QObject: Timers cannot be stopped from another thread

Then everything crashes and the output video is just the first video, with no sound. What is my error?

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