Question: "solve" give 0 but should give something else

Hi everybody.

> deq := m*(diff(v(t), t)) = m*g-k*v(t);

                              / d      \               
                     deq := m |--- v(t)| = m g - k v(t)
                              \ dt     /               
> ci := v(0) = v0;

                               ci := v(0) = v0
> dsolve({ci, deq}, v(t));

                            m g      /  k t\ /     m g\
                     v(t) = --- + exp|- ---| |v0 - ---|
                             k       \   m / \      k /
> solv := rhs(%);

                             m g      /  k t\ /     m g\
                     solv := --- + exp|- ---| |v0 - ---|
                              k       \   m / \      k /
> solx := int(solv, t = 0 .. t)+C;

              /                        /  k t\           /  k t\    \    
            m |v0 k - m g + g t k - exp|- ---| v0 k + exp|- ---| m g|    
              \                        \   m /           \   m /    /    
    solx := --------------------------------------------------------- + C
                                        2                                
                                       k                                 
> subs(t = 0, solx) = 0;

              m (v0 k - m g - exp(0) v0 k + exp(0) m g)        
              ----------------------------------------- + C = 0
                                  2                            
                                 k                             
> solve(%, C);

                                      0

?????????????

Mario