diff --git a/png.h b/png.h
index d10fd29..9bb53f8 100644
--- a/png.h
+++ b/png.h
@@ -1,7 +1,7 @@
 
 /* png.h - header file for PNG reference library
  *
- * libpng version 1.5.3beta08 - May 11, 2011
+ * libpng version 1.5.3beta08 - May 13, 2011
  * Copyright (c) 1998-2011 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
@@ -11,7 +11,7 @@
  * Authors and maintainers:
  *   libpng versions 0.71, May 1995, through 0.88, January 1996: Guy Schalnat
  *   libpng versions 0.89c, June 1996, through 0.96, May 1997: Andreas Dilger
- *   libpng versions 0.97, January 1998, through 1.5.3beta08 - May 11, 2011: Glenn
+ *   libpng versions 0.97, January 1998, through 1.5.3beta08 - May 13, 2011: Glenn
  *   See also "Contributing Authors", below.
  *
  * Note about libpng version numbers:
@@ -182,7 +182,7 @@
  *
  * This code is released under the libpng license.
  *
- * libpng versions 1.2.6, August 15, 2004, through 1.5.3beta08, May 11, 2011, are
+ * libpng versions 1.2.6, August 15, 2004, through 1.5.3beta08, May 13, 2011, are
  * Copyright (c) 2004, 2006-2011 Glenn Randers-Pehrson, and are
  * distributed according to the same disclaimer and license as libpng-1.2.5
  * with the following individual added to the list of Contributing Authors:
@@ -294,7 +294,7 @@
  * Y2K compliance in libpng:
  * =========================
  *
- *    May 11, 2011
+ *    May 13, 2011
  *
  *    Since the PNG Development group is an ad-hoc body, we can't make
  *    an official declaration.
@@ -357,7 +357,7 @@
 /* Version information for png.h - this should match the version in png.c */
 #define PNG_LIBPNG_VER_STRING "1.5.3beta08"
 #define PNG_HEADER_VERSION_STRING \
-     " libpng version 1.5.3beta08 - May 11, 2011\n"
+     " libpng version 1.5.3beta08 - May 13, 2011\n"
 
 #define PNG_LIBPNG_VER_SONUM   15
 #define PNG_LIBPNG_VER_DLLNUM  15
@@ -1400,7 +1400,11 @@
 #endif
 
 #ifdef PNG_READ_BACKGROUND_SUPPORTED
-/* Handle alpha and tRNS by replacing with a background color. */
+/* Handle alpha and tRNS by replacing with a background color.  Prior to
+ * libpng-1.5.3 this API must not be called before the PNG file header has been
+ * read.  Doing so will result in unexpected behavior and possible warnings or
+ * errors int the PNG file contains a bKGD chunk.
+ */
 PNG_FP_EXPORT(47, void, png_set_background, (png_structp png_ptr,
     png_const_color_16p background_color, int background_gamma_code,
     int need_expand, double background_gamma));