Recently, Jakse and Pasturel [J. Chem. Phys.129, 104503 (2008)] using first principles molecular dynamics simulations reported evidence for a fragile-to-strong transition in supercooled liquid Si. This conclusion was based on the presence (absence) of a Boson peak in the low-density, strong liquid (high-density, fragile liquid) phase. Based on existing experimental data it is pointed out that (i) the assignment of the Boson peak in the above reference is erroneous and (ii) the Boson peak strength is not generally useful for determining the strong or fragile character of a supercooled liquid. Therefore, the inference that liquid-liquid phase transition in supercooled liquid Si is a fragile-to-strong transition is unjustifiable.