diff --git a/src/version.c b/src/version.c
index 80c9fe3..818a8b5 100644
--- a/src/version.c
+++ b/src/version.c
@@ -735,6 +735,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    280,
+/**/
     279,
 /**/
     278,
diff --git a/src/window.c b/src/window.c
index 02eb903..485f7ef 100644
--- a/src/window.c
+++ b/src/window.c
@@ -5623,7 +5623,7 @@
     win_T	*wp;
 {
     wp->w_fraction = ((long)wp->w_wrow * FRACTION_MULT
-				    + FRACTION_MULT / 2) / (long)wp->w_height;
+				    + wp->w_height / 2) / (long)wp->w_height;
 }
 
 /*
@@ -5638,6 +5638,7 @@
 {
     linenr_T	lnum;
     int		sline, line_size;
+    int		prev_height = wp->w_height;
 
     /* Don't want a negative height.  Happens when splitting a tiny window.
      * Will equalize heights soon to fix it. */
@@ -5646,8 +5647,13 @@
     if (wp->w_height == height)
 	return;	    /* nothing to do */
 
-    if (wp->w_wrow != wp->w_prev_fraction_row && wp->w_height > 0)
-	set_fraction(wp);
+    if (wp->w_height > 0)
+    {
+	if (wp == curwin)
+	    validate_cursor();		/* w_wrow needs to be valid */
+	if (wp->w_wrow != wp->w_prev_fraction_row)
+	    set_fraction(wp);
+    }
 
     wp->w_height = height;
     wp->w_skipcol = 0;
@@ -5667,7 +5673,8 @@
 	lnum = wp->w_cursor.lnum;
 	if (lnum < 1)		/* can happen when starting up */
 	    lnum = 1;
-	wp->w_wrow = ((long)wp->w_fraction * (long)height - 1L) / FRACTION_MULT;
+	wp->w_wrow = ((long)wp->w_fraction * (long)height - 1L
+					 + FRACTION_MULT / 2) / FRACTION_MULT;
 	line_size = plines_win_col(wp, lnum, (long)(wp->w_cursor.col)) - 1;
 	sline = wp->w_wrow - line_size;
 
@@ -5757,7 +5764,8 @@
 	    update_topline();
 	curs_columns(FALSE);	/* validate w_wrow */
     }
-    wp->w_prev_fraction_row = wp->w_wrow;
+    if (prev_height > 0)
+	wp->w_prev_fraction_row = wp->w_wrow;
 
     win_comp_scroll(wp);
     redraw_win_later(wp, SOME_VALID);