In order to test the fitting method, the procedure was used to fit an ωB97X-D3(BJ) type hybrid (without UW12). Fitting all possible combinations of parameters and analyzing the weighted error in the validation set results in the best possible functional with 8 linear parameters (see figure ). When the procedure was repeated with the UW12 components included, the optimal number of parameters was found to be around 15. However, the fitted B97 coefficients for these functional combinations were found to be significantly larger than those present in the non-UW12 fitted functionals. While this effect was significantly reduced if our search was limited to combinations where higher order B97 terms are only included if all lower order terms are already present for each series expansion -where no B97 components were skipped. The coefficients were still significantly greater than in the non-UW12 functional.