We apply the K-correction to the black hole low-mass X-ray binary (LMXB) GX 339-4 which implies MX >= 6Msolar by only assuming that the companion is more massive than ~0.17Msolar, the lower limit allowed by applying a `stripped-giant' model. This evolutionary model successfully reproduces the observed properties of the system. We obtain a maximum mass for the companion of M2 <= 1.1Msolar and an upper limit to the mass ratio of q(=M2/MX) <= 0.125. The high X-ray activity displayed by the source suggests a relatively large mass transfer rate which, according to the model, results in M2 >~ 0.3Msolar and MX >~ 7Msolar. We have also applied this scenario to the black hole binary XTE J1550-564, which has a similar orbital period but the donor is detected spectroscopically. The model successfully reproduces the observed stellar parameters.