```
data abc;
  a = 1; output;
  a = 99; output;
run;

proc format; 
  invalue abc
    99 = .
    other = _same_;

      value abc
    99 = .
    other = _same_;
run;

proc means data = abc;
    format a abc.;
    informat a abc.;
    var a;
run;

```

I would expect the above code to give me a mean of 1 for the variable a. But it doesn't, in proc means it doesn't seem to want to use the format I have defined. Is there an option I can turn on to make it work?