It is important for investors to know not only the style of a fund manager in which they are interested, but also whether this style is constant or changing through time. The style of a fund manager can be estimated by the so-called style regression, and a great deal of research has been carried out to investigate the statistical properties of style regression methods. However, there has been no formal and statistically valid method to test for a change in manager style when the two typically imposed restrictions (sum-to-one and non-negativity) are jointly present in style analysis. In this study, we apply and extend the results of Andrews (Econometrica 61:821-856, 1993; Estimation when a parameter is on a boundary: theory and application, Yale University, 1997a; A simple counterexample to the bootstrap,