Index: src/ex_cmds.c
===================================================================
--- src/ex_cmds.c	(revision 57778)
+++ src/ex_cmds.c	(working copy)
@@ -4069,7 +4069,7 @@
     if (eap->forceit)
 	bigness = curwin->w_height;
     else if (firstwin == lastwin)
-	bigness = curwin->w_p_scr * 2;
+	bigness = p_window_unix2003 ? p_window_unix2003 : curwin->w_p_scr * 2;
 #ifdef FEAT_WINDOWS
     else
 	bigness = curwin->w_height - 3;