<unknown>parser error

[ghost]

I sbt-assembled the jar and this is what i get when trying to use it

java -jar scalabuff-compiler-assembly-1.4.0.jar --proto_path=. --scala_out=.
<unknown>:1:1: string matching regex `\z' expected but `s' found
syntax = "proto3";
^
<unknown>:1:1: string matching regex `\z' expected but `s' found
syntax = "proto3";
^

the .proto file is a minimal example (regardless of whether using proto2 or 3 syntax, and yes, it throws two of the same errors for one file)

syntax = "proto3";
message Example{
  required int32 test = 1;
}