The standard Vasicek credit loss model assumes a constant probability of default. We extend it to allow the default probability to depend on macroeconomic factors and show that maximum likelihood estimates of all parameters, including the asset value correlation, reduce to a probit-transformed OLS regression with a simple algebraic recovery step. The estimator is exact, closed-form, and extends naturally to any number of factors. We illustrate the approach with an example, and discuss bias correction for small samples.