Recently Yousefi and Hesameddini  have obtained a characterization for shift invariant subspaces of a special class of Hilbert spaces contained in the Hardy space H2. In the present note we settle an open problem posed by them in their paper. In fact, by discussing invariance under multiplication by finite Blaschke factors we prove a far more general result than the main result of . We prove our results under much weaker assumptions than the assumptions of  and with a simpler proof. © 2011 The Japan Academy.