We consider VuQ model which involves addition of a vector isosinglet t' quark to the standard model. In this model the full CKM quark mixing matri× is 4 × 3. Using present flavor-physics data, we perform a fit to this full CKM matrix. We find that the current flavor data puts stringent constraints on the VuQ model. There are no hints of new physics in the CKM matrix. Furthermore, the fit to the data indicates that any new physics contributions to b → s, b → d and s → d transitions are very small. There can be significant enhancements of the branching ratios of t → uZ and t → cZ decays, but these are still below present detection levels. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0).