Adobe Premiere saves m4v instead of mp4 I have problems with my Premiere Pro. It is first time this has happened, and I cannot understand why. 

I am creating a timelapse from my images. When I want to export media, I choose format H.264 (not H.264 Blu-ray), dimensions 1920x1080. Output name is visible as "Sequence02.mp4". 

After export is finished, there is a file "Sequence02.m4v" on disk. Why? What causes Premiere to change file format by itself? I used Premiere before and this never happened. Maybe I'm using some different setting, but what could cause this change?
I encountered the same issue when I turned the sound off in the sequence.  When I re-enabled audio export, even though I didn't want to or need to, it saved as an mp4 again.