In a paper from 2016 D. R. Yafaev considers Hankel operators associated with Hamburger moment sequences q_n and claims that the corresponding Hankel form is closable if and only if the moment sequence tends to 0. The claim is not correct, since we prove closability for any indeterminate moment sequence but also for certain determinate moment sequences corresponding to measures with finite index of determinacy. In an Erratum Yafaev (Integr Equ Oper Theory, to appear) has proved the result under quasi-analyticity assumptions, which imply that the moment sequence is determinate.