  We prove the existence and uniqueness of a mild solution for a class of
non-autonomous parabolic mixed stochastic partial differential equations
defined on a bounded open subset $D \subset \mathbb{R}^d$ and involving
standard and fractional $L^2(D)$-valued Brownian motions. We assume that the
coefficients are homogeneous, Lipschitz continuous and the coefficient at the
fractional Brownian motion is an affine function.
