Problem to plot vector fields (Stokes problem)

Hello all,

I am solving the Stokes Problem,


// Fespace
fespace Uh(ThRef, P1b);
Uh u, v;
Uh uu, vv;

fespace Ph(ThRef, P1);
Ph p, pp;

// Problem
solve stokes ([u, v, p], [uu, vv, pp])
     = int2d(ThRef)(
          dx(u)*dx(uu)
         + dy(u)*dy(uu)
         + dx(v)*dx(vv)
         + dy(v)*dy(vv)
         + dx(p)*uu
         + dy(p)*vv
         + pp*(dx(u) + dy(v))
         - 1e-10*p*pp
     )
     + on(lab0, u=0, v=0)
     + on(20, u=1, v=0)
     ;


// Plot
plot([u,v],p, wait=1);

However when I want to plot the vector field I have this following error:

 Error line number 48, in file ReferenceStokes.edp, before  token )
plot of array with wrong  number of components (!= 2 or 3) 
  current line = 48
Compile error : plot of array with wrong  number of components (!= 2 or 3) 
	line number :48, )
error Compile error : plot of array with wrong  number of components (!= 2 or 3) 
	line number :48, )
 code = 1 mpirank: 0

The plot works well when I plot component by component.

Could someone know how to solve this problem ?

Thank you in advance,

Best regards,

Loïc,