--- rxvt-unicode/src/screen.C	2011/07/07 23:15:44	1.386
+++ rxvt-unicode/src/screen.C	2011/07/08 00:23:22	1.389
@@ -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)
         {
@@ -736,6 +736,14 @@
       // use a simple and robust scrolling algorithm, this
       // part of scr_scroll_text is not time-critical.
 
+      // sever line above scroll region
+      if (row1)
+        {
+          line_t &l = ROW(row1 - 1);
+          l.is_longer (0);
+          l.touch ();
+        }
+
       int rows = row2 - row1 + 1;
 
       min_it (count, rows);
@@ -752,6 +760,14 @@
 
       for (int row = 0; row < rows; row++)
         ROW(row1 + row) = temp_buf [row];
+
+      // sever bottommost line
+      {
+        line_t &l = ROW(row2 - 1);
+        l.is_longer (0);
+        l.touch ();
+      }
+
     }
 
   return count;