error when attempting concat

[Nitzahon]

I received the following error when trying to concat 2 files: Input #0, matroska,webm, from 'concat:60b87d7632e1c624fcd09ce1.mp3|60b87d7932e1c624fcd09ce3.mp3': Metadata: encoder : Chrome Duration: N/A, start: 0.000000, bitrate: N/A Stream #0:0(eng): Audio: opus, 48000 Hz, mono, fltp (default) [mp3 @ 0000025dbb9f5780] Invalid audio stream. Exactly one MP3 audio stream is required. Could not write header for output file #0 (incorrect codec parameters ?): Invalid argument Stream mapping: Stream #0:0 -> #0:0 (copy) Last message repeated 1 times