Time-dependent DirichletBC and enriched elements

Hello.

I have a problem with time-dependent Dirichlet boundary conditions on an enriched subspace of a mixed function space.
The spaces are defined as (MINI elements)

P1 = FiniteElement('Lagrange', mesh.ufl_cell(), 1)
B = FiniteElement('Bubble', mesh.ufl_cell(), 1 + ndim)
W = FunctionSpace(mesh, MixedElement(ndim*[P1 + B])*P1)

I have a DirichletBC, defined via a time dependent Expression, say

inflow = Expression(('sin(DOLFIN_PI*t)', '0'), t=0)

on W.sub(0), which I have to project, because "evaluate_dof(s) for enriched element not implemented":

inflow_proj = project(inflow, W.sub(0).collapse())

THIS, however, makes it necessary to project and redefine the DirichletBC at every timestep after updating the expression via inflow.t = t, significantly increasing the computation time.

Is there any way to circumvent this?

Thanks!
David