--- rxvt-unicode/src/screen.C	2011/07/07 23:18:13	1.387
+++ rxvt-unicode/src/screen.C	2011/07/08 00:08:40	1.388
@@ -640,24 +640,36 @@
       && row1 == 0
       && (current_screen == PRIMARY || option (Opt_secondaryScroll)))
     {
-      min_it (count, row2 + total_rows);
+      min_it (count, total_rows - (nrow - (row2 + 1)));
 
       top_row = max (top_row - count, -saveLines);
 
-      // scroll everything up 'count' lines
-      term_start = (term_start + count) % total_rows;
-
       // sever bottommost line
       {
-        line_t &l = ROW(row2 - count);
+        line_t &l = ROW(row2 - 1);
         l.is_longer (0);
         l.touch ();
       }
 
+      // scroll everything up 'count' lines
+      term_start = (term_start + count) % total_rows;
+
+      // now copy lines below the scroll region bottom to the
+      // bottom of the screen again, so they look as if they
+      // hadn't moved.
+      for (int i = nrow; --i > row2; )
+        {
+          line_t &l1 = ROW(i - count);
+          line_t &l2 = ROW(i);
+
+          ::swap (l1, l2);
+          l2.touch ();
+        }
+
       // erase newly scrolled-in lines
       for (int i = count; i--; )
         {
-          line_t &l = ROW(nrow - 1 - i);
+          line_t &l = ROW(row2 - i);
 
           // optimise if already cleared, can be significant on slow machines
           // could be rolled into scr_blank_screen_mem
@@ -671,18 +683,6 @@
             scr_blank_screen_mem (l, rstyle);
         }
 
-      // now copy lines below the scroll region bottom to the
-      // bottom of the screen again, so they look as if they
-      // hadn't moved.
-      for (int i = nrow; --i > row2; )
-        {
-          line_t &l1 = ROW(i - count);
-          line_t &l2 = ROW(i);
-
-          ::swap (l1, l2);
-          l2.touch ();
-        }
-
       // move and/or clear selection, if any
       if (selection.op && current_screen == selection.screen)
         {