--- gcc/opts.c.mp	2013-01-04 02:48:33.116785922 +0100
+++ gcc/opts.c	2013-01-04 02:48:51.729870314 +0100
@@ -1,7 +1,6 @@
 /* Command line option handling.
    Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011,
-   2012
-
+   2012, 2013
    Free Software Foundation, Inc.
    Contributed by Neil Booth.
 
@@ -543,7 +542,8 @@ default_options_optimization (struct gcc
 	      const int optimize_val = integral_argument (opt->arg);
 	      if (optimize_val == -1)
 		error_at (loc,
-			  "argument to %qs should be a non-negative integer",
+			  "argument to %qs should be a non-negative integer, "
+			  "'g', 's', or 'fast'",
 			  "-O");
 	      else
 		{