  We give a bicategorical version of the main result of A. Masuoka ({Corings
and invertible bimodules,} {\em Tsukuba J. Math.} \textbf{13} (1989), 353--362)
which proposes a non-commutative version of the fact that for a faithfully flat
extension of commutative rings $R \subseteq S$, the relative Picard group
$Pic(S/R)$ is isomorphic to the Amitsur 1--cohomology group $H^1(S/R,U)$ with
coefficients in the units functor $U$.
