--- xscreensaver-5.11/hacks/xjack.c.small 2008-07-31 18:52:05.000000000 +0900
+++ xscreensaver-5.11/hacks/xjack.c 2010-06-28 02:42:42.000000000 +0900
@@ -59,6 +59,10 @@
XGetWindowAttributes (st->dpy, st->window, &st->xgwa);
st->columns = (st->xgwa.width - st->hspace - st->hspace) / st->char_width;
st->rows = (st->xgwa.height - st->vspace - st->vspace) / st->line_height;
+ /* If the window is stupidly small, just truncate. */
+ if (st->rows < 4) st->rows = 4;
+ if (st->columns < 12) st->columns = 12;
+
st->rows--;
st->columns--;