My son is 25 year old full time student. As per IRS Child Test, he does not qualify as a dependent as he is over 24. However, in Turbo Tax marked him as dependent.

My son is 25 year old full time student. As per IRS Child Test,  he does not qualify as a dependent as he is over 24. However,  in Turbo Tax ->  Personal Info -> Dependents  interview questions,  Turbo Tax determined him as a Dependent as his income is less than $4,400, he is full time student, lived with me whole year, unmarried. 
Question - why does Turbo Tax fail age test?