Subject gfix gives "data page error" but errorlevel 0

I have a database that is having problems. (Trying to back it up gives errors.) 

When I run gfix -v -n -full on it, I get:

Summary of validation errors

        Number of data page errors      : 1

But the errorlevel return from gfix is 0, indicating no error. 

I have actually replaced gfix in my application by my own DLL using the Services API, and it's having the same problem - it return 0, thinking there is no error.

What is going out, that there is apparent error output but an errorlevel / return value of 0? Is there something I could change in my Services API C code to catch that error even though all of the calls seem to have succeeded as expected?