Issue parsing OBJ file from Wings3d

[busterbogheart]

I've set up the example project in Android Studio 4.1.2 and built it successfully. Then I attempted to load my own (simple) model:

I/flutter (32680): ----- -----_parseMtl START
I/flutter (32680): ----- -----_parseMtl END
I/flutter (32680): ----- -----_parseObj START
I/flutter (32680): ----- -----_parseObj usemtl default
E/flutter (32680): [ERROR:flutter/lib/ui/ui_dart_state.cc(177)] Unhandled Exception: FormatException: Invalid number (at character 1)
E/flutter (32680): 
E/flutter (32680): ^
E/flutter (32680): 
E/flutter (32680): #0      int._throwFormatException (dart:core-patch/integers_patch.dart:129:7)

What are the requirements for a OBJ model to be loaded successfully?