Unable to upload m4a files

Unable to upload m4a files getting an error "file type isn't allowed" Issue happens on all content types that allow uploading of audio files. I tried different m4a files from different sources and I get the error message on all of them.

Issue is reported here: https://h5p.org/node/642262/

This may be related to this ticket: https://h5ptechnology.atlassian.net/browse/HFP-2879