1 files changed, 15 insertions, 4 deletions

diff --git a/src/msdos.c b/src/msdos.c
index f26ddd868a3..85ff6dd94a6 100644
--- a/src/msdos.c
+++ b/src/msdos.c
@@ -1360,6 +1360,11 @@ fast_find_position (struct window *w, int pos, int *hpos, int *vpos)
         }
       else if (line_start_position > 0)
         best_row = row;
+
+      /* Don't overstep the last matrix row, lest we get into the
+         never-never land... */
+      if (row->y + 1 >= yb)
+        break;
       
       ++row;
     }
@@ -1456,7 +1461,7 @@ static void
 IT_note_mouse_highlight (struct frame *f, int x, int y)
 {
   struct display_info *dpyinfo = FRAME_X_DISPLAY_INFO (f);
-  int portion;
+  int portion = -1;
   Lisp_Object window;
   struct window *w;
 
@@ -1515,16 +1520,22 @@ IT_note_mouse_highlight (struct frame *f, int x, int y)
       && (XFASTINT (w->last_overlay_modified)
           == BUF_OVERLAY_MODIFF (XBUFFER (w->buffer))))
     {
-      int pos, i, area;
+      int pos, i;
       struct glyph_row *row;
       struct glyph *glyph;
+      int nrows = w->current_matrix->nrows;
 
       /* Find the glyph under X/Y.  */
       glyph = NULL;
-      if (y < w->current_matrix->nrows)
+      if (y >= 0 && y < nrows)
         {
           row = MATRIX_ROW (w->current_matrix, y);
-          if (row->enabled_p
+          /* Give up if some row before the one we are looking for is
+             not enabled.  */
+          for (i = 0; i <= y; i++)
+            if (!MATRIX_ROW (w->current_matrix, i)->enabled_p)
+              break;
+          if (i > y  /* all rows upto and including the one at Y are enabled */
               && row->displays_text_p
               && x <  window_box_width (w, TEXT_AREA))
             {