How to use fopen with Simulink and Matlab Coder in 2013A ?

As far as I understand, fopen, fprintf and fclose are supported for code generation from Matlab R2013A. I'm currently using that exact version and I'm having a hard time generating C code for a Simulink model where those 3 functions are used to write in a text file via a Matlab embedded function. The model is set to run in accelerator mode.

Here's the code of the function:

function fcn(arg1, arg2, arg3, arg4, arg5)
  fileID = fopen('output.txt', 'a');
  fprintf(fileID, '%10.1f %10.5f %10.3f %10.6f %10.3f\n', arg1, arg2, arg3, arg4, arg5);
  fclose(fileID);
end

When attempting to generate, an error message mentions a failure to parse that function. What am I doing wrong? Or is this a bug of Matlab Coder?