Regularization is a technique generally used to prevent overfitting to data. There are multiple forms of regularization that can be applied to improve fitting. In this work we use a harmonic restraint that is added to the error function. This penalty term ensures that torsional parameters do not deviate significantly from their initial value unless a significant improvement in the agreement with the QM energy surface is observed. As we will show, even with low levels of regularization (a small λ value), a sizeable increase in performance is observed for the QUBE force field. The general form of the error function used in this study is given by: