Hmm unsure, it works here on Windows as well. So Let's take a look at the source:
So, it looks like its first chance to return a bad argument error is at:
Thus that can only happen if a non-int64 was passed in, and your number is static and smaller, so it should be fine.
And, hmm, I'm not seeing any other badarg calls anywhere else down in to its callstack...
That makes me wonder, is Erlang a 32-bit or 64-bit on your laptop? Is Erlang a 32-bit or 64-bit on your dokku-thing?