  Let $R$ be a ring and denote by $\mathcal{FM}$ the class of all flat and
Mittag-Leffler left $R$-modules. In \cite{BazzoniStovicek2} it is proved that,
if $R$ is countable, the orthogonal class of $\mathcal{FM}$ consists of all
cotorsion modules. In this note we extend this result to the class of all rings
$R$ satisfying that each flat left $R$-module is filtered by totally ordered
limits of projective modules. This class of rings contains all countable, left
perfect and discrete valuation domains. Moreover, assuming that there do not
exist inaccessible cardinals, we obtain that, over these rings, all flat left
$R$-modules have finite projective dimension.
