Are contexts broken



I can't make sense of this output,

Rich


(%i1) newcontext(pwz);
(out1)     pwz
(%i2) activate(pwz);
(out2)     done
(%i3) assume(x>0);
(out3)     [x > 0]
(%i4) facts(pwz);
(out4)     [x > 0]
(%i5) kill(global);
(out5)      done
(%i6) facts(pwz);
(out6) [x > 0]
(%i7) deactivate(pwz);
(out7) done
(%i8) facts(pwz);
(out8) [x > 0]
(%i9) is(x>0);
(out9)  true
(%i10) killcontext(pwz);
(out10) done
(%i11) is(x>0);
(out11)unknown
(%i12)