old code not working anymore



I just noticed that some old (3-4 years old) maxima code I had written
doesn't work anymore. It's using the dynamics package

Here it is

--8<---------------cut here---------------start------------->8---
/* [wxMaxima: input   start ] */
load(dynamics)$load(draw)$
/* [wxMaxima: input   end   ] */

/* [wxMaxima: input   start ] */
Epot(x):=.5*x^2$
F(x):=-diff(Epot(x),x)$
/* [wxMaxima: input   end   ] */

/* [wxMaxima: input   start ] */
context :aperiodique$assume(Q>0,Q<1/2)$
/* [wxMaxima: input   end   ] */

/* [wxMaxima: input   start ] */
context : pseudoperiodique;assume(Q> 1/2);
/* [wxMaxima: input   end   ] */

/* [wxMaxima: input   start ] */
x0 : 1$ v0 : 0$
/* [wxMaxima: input   end   ] */

/* [wxMaxima: input   start ] */
kill(Q)$context : pseudoperiodique $
sol : ic2(ode2('diff(x,t,2)+'diff(x,t)/Q+x=0,x,t),t=0,x=x0,dy=v0);
/* [wxMaxima: input   end   ] */

--8<---------------cut here---------------end--------------->8---

I get the following error message?:

diff: variable must not be a number; found : 0

Thanks for your help,

Julien.