[FFmpeg-user] -map and matroska files

[Marios Titas]

Hi all,

I have a video file with multiple audio streams and I want to select
one of them. I did

    ffmpeg -i input.mkv -map 0.0 -map 0.2 -y output.avi

to select streams 0 (the video) and 2 (the desired audio stream) and
this works fine. But if I try to output to matroska, ie

    ffmpeg -i input.mkv -map 0.0 -map 0.2 -y output.mkv

this fails with the following error:

    Number of stream maps must match number of output streams

Why is this happening?