Why do I get error "'SS_OPTIO​N_CALL_TER​MINATE_ON_​EXIT' undeclared (first use in this function)" when trying to compile an S function ?

Hello

I am trying to compile the source code of an s function with the option SS_OPTION_CALL_TERMINATE_ON_EXIT inside of the mdlInitializeSizes function. I have included simstruc.h at the start of the function and everything else was done properly to my knowledge, since the function compiled perfectly fine previously, before I tried to set any options. The code for mdlInitializeSizes is shown below:

static void mdlInitializeSizes(SimStruct *S)
{
  /* Number of expected parameters--normally 0 */
  ssSetNumSFcnParams(S, 0);
  
  /* Return if number of expected != number of actual parameters */
  if (ssGetNumSFcnParams(S) != ssGetSFcnParamsCount(S))
      return;

  ssSetNumContStates(    S, ntot);  /* number of continuous states            */
  ssSetNumDiscStates(    S, 1);     /* number of discrete states              */
  ssSetNumInputs(        S, ninpt); /* number of inputs                       */
  ssSetNumOutputs(       S, nout);  /* number of outputs                      */
  ssSetDirectFeedThrough(S, 1);     /* direct feedthrough flag                */
  ssSetNumSampleTimes(   S, 1);     /* number of sample times                 */
  ssSetNumRWork(         S, 0);     /* number of real work vector elements    */
  ssSetNumIWork(         S, 0);     /* number of integer work vector elements */
  ssSetNumPWork(         S, 0);     /* number of pointer work vector elements */
  ssSetNumModes(         S, 0);     /* number of mode work vector elements    */
  ssSetNumNonsampledZCs( S, 0);     /* number of nonsampled zero crossings    */
  ssSetOptions(S,SS_OPTION_CALL_TERMINATE_ON_EXIT);     /* general options (SS_OPTION_xx)         */
}

The entire code is very long (~3000 lines) and includes other library files to compile, so I don't think I can include it, besides the rest of the code compiled fine in the past. I used to set:

ssSetOptions(S,0);

and the code compiled without any problems, but now I need to use some of the options to try and troubleshoot a different problem with the code. I would really appreciate some help, I am not sure why this isn't working, I thought the option names were recognised by the compiler.