If j : Xj !Rn, j ¼ 1, 2, are domains over Rn, then ¼ X1 X2 carries a canonical structure of a generalized tube domain over Cn. In response to a question of Jarnicki and Pflug (M. Jarnicki and P. Pflug (2000). Extension of Holomorphic Functions, Springer-Verlag), we show that is one-sheeted and equivalent to a product of convex domains, if it is pseudoconvex.