--- xscreensaver-5.11/hacks/xjack.c.small	2008-07-31 18:52:05.000000000 +0900
+++ xscreensaver-5.11/hacks/xjack.c	2010-07-26 02:33:17.000000000 +0900
@@ -62,6 +62,10 @@
   st->rows--;
   st->columns--;
 
+  /* If the window is stupidly small, just truncate. */
+  if (st->rows < 4)     st->rows = 4;
+  if (st->columns < 12) st->columns = 12;
+
   if (st->y > st->rows)    st->y = st->rows-1;
   if (st->x > st->columns) st->x = st->columns-2;
 
@@ -116,9 +120,12 @@
 
   xjack_reshape (dpy, window, st, st->xgwa.width, st->xgwa.height);
 
-  st->left = 0xFF & (random() % ((st->columns / 2)+1));
-  st->right = st->left + (0xFF & (random() % (st->columns - st->left - 10)
+  if (st->columns >= 21)
+  {
+    st->left = 0xFF & (random() % ((st->columns / 2)+1));
+    st->right = st->left + (0xFF & (random() % (st->columns - st->left - 10)
                                   + 10));
+  }
   st->x = 0;
   st->y = 0;