Cannot set atempo to float value in macOS

[gernophil]

Hey everyone,
if I set the ff_opts dict to the following values, it raises an error:

ff_opts = {'ss': start / 1000, 'af':'atempo=1.2', 'vn':True}
MediaPlayer(self.audio_source, ff_opts=ff_opts, callback=self.ffplay_callback)

[Parsed_atempo_0 @ 0x600001b079c0] [Eval @ 0x16b9f9ed8] Invalid chars '.2' at the end of expression '1.2'
[Parsed_atempo_0 @ 0x600001b079c0] Unable to parse option value "1.2"
[Parsed_atempo_0 @ 0x600001b079c0] Error setting option tempo to value 1.2.

Somehow it's not able to read the dot from the float correctly. Running this on Windows works. Any ideas?