diff --git a/png.h b/png.h
index 76f9fe09..f309a699 100644
--- a/png.h
+++ b/png.h
@@ -1,6 +1,6 @@
 /* png.h - header file for PNG reference library
  *
- * libpng version 1.2.40beta01 - August 13, 2009
+ * libpng version 1.2.40beta01 - August 19, 2009
  * Copyright (c) 1998-2009 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.)
@@ -10,7 +10,7 @@
  * 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 1.2.40beta01 - August 13, 2009: Glenn
+ *  libpng versions 0.97, January 1998, through 1.2.40beta01 - August 19, 2009: Glenn
  *  See also "Contributing Authors", below.
  *
  * Note about libpng version numbers:
@@ -273,7 +273,7 @@
  *
  * This code is released under the libpng license.
  *
- * libpng versions 1.2.6, August 15, 2004, through 1.2.40beta01, August 13, 2009, are
+ * libpng versions 1.2.6, August 15, 2004, through 1.2.40beta01, August 19, 2009, are
  * Copyright (c) 2004, 2006-2009 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:
@@ -385,7 +385,7 @@
  * Y2K compliance in libpng:
  * =========================
  *
- *    August 13, 2009
+ *    August 19, 2009
  *
  *    Since the PNG Development group is an ad-hoc body, we can't make
  *    an official declaration.
@@ -449,7 +449,7 @@
 /* Version information for png.h - this should match the version in png.c */
 #define PNG_LIBPNG_VER_STRING "1.2.40beta01"
 #define PNG_HEADER_VERSION_STRING \
-   " libpng version 1.2.40beta01 - August 13, 2009\n"
+   " libpng version 1.2.40beta01 - August 19, 2009\n"
 
 #define PNG_LIBPNG_VER_SONUM   0
 #define PNG_LIBPNG_VER_DLLNUM  13
@@ -490,11 +490,11 @@
 #define PNG_LIBPNG_VER 10240 /* 1.2.40 */
 
 #ifndef PNG_VERSION_INFO_ONLY
-/* include the compression library's header */
+/* Include the compression library's header */
 #include "zlib.h"
 #endif
 
-/* include all user configurable info, including optional assembler routines */
+/* Include all user configurable info, including optional assembler routines */
 #include "pngconf.h"
 
 /*
@@ -576,7 +576,7 @@ extern "C" {
  */
 #ifdef PNG_USE_GLOBAL_ARRAYS
 PNG_EXPORT_VAR (PNG_CONST char) png_libpng_ver[18];
-  /* need room for 99.99.99beta99z */
+  /* Need room for 99.99.99beta99z */
 #else
 #define png_libpng_ver png_get_header_ver(NULL)
 #endif
@@ -786,7 +786,7 @@ typedef png_unknown_chunk FAR * FAR * png_unknown_chunkpp;
  */
 typedef struct png_info_struct
 {
-   /* the following are necessary for every PNG file */
+   /* The following are necessary for every PNG file */
    png_uint_32 width;       /* width of image in pixels (from IHDR) */
    png_uint_32 height;      /* height of image in pixels (from IHDR) */
    png_uint_32 valid;       /* valid chunk data (see PNG_INFO_ below) */
@@ -1191,10 +1191,10 @@ typedef void (PNGAPI *png_unknown_chunk_ptr) PNGARG((png_structp));
 #define PNG_TRANSFORM_SWAP_ALPHA     0x0100    /* read and write */
 #define PNG_TRANSFORM_SWAP_ENDIAN    0x0200    /* read and write */
 #define PNG_TRANSFORM_INVERT_ALPHA   0x0400    /* read and write */
-#define PNG_TRANSFORM_STRIP_FILLER   0x0800    /* WRITE only, deprecated */
+#define PNG_TRANSFORM_STRIP_FILLER   0x0800    /* write only, deprecated */
 /* Added to libpng-1.2.34 */
-#define PNG_TRANSFORM_STRIP_FILLER_BEFORE 0x0800  /* WRITE only */
-#define PNG_TRANSFORM_STRIP_FILLER_AFTER  0x1000  /* WRITE only */
+#define PNG_TRANSFORM_STRIP_FILLER_BEFORE 0x0800  /* write only */
+#define PNG_TRANSFORM_STRIP_FILLER_AFTER  0x1000  /* write only */
 
 /* Flags for MNG supported features */
 #define PNG_FLAG_MNG_EMPTY_PLTE     0x01
@@ -1435,7 +1435,7 @@ struct png_struct_def
 #if defined(PNG_MNG_FEATURES_SUPPORTED) || \
     defined(PNG_READ_EMPTY_PLTE_SUPPORTED) || \
     defined(PNG_WRITE_EMPTY_PLTE_SUPPORTED)
-/* changed from png_byte to png_uint_32 at version 1.2.0 */
+/* Changed from png_byte to png_uint_32 at version 1.2.0 */
 #ifdef PNG_1_0_X
    png_byte mng_features_permitted;
 #else
@@ -2091,7 +2091,7 @@ extern PNG_EXPORT(png_voidp,png_get_progressive_ptr)
 extern PNG_EXPORT(void,png_process_data) PNGARG((png_structp png_ptr,
    png_infop info_ptr, png_bytep buffer, png_size_t buffer_size));
 
-/* function that combines rows.  Not very much different than the
+/* Function that combines rows.  Not very much different than the
  * png_combine_row() call.  Is this even used?????
  */
 extern PNG_EXPORT(void,png_progressive_combine_row) PNGARG((png_structp png_ptr,
@@ -2997,7 +2997,7 @@ extern PNG_EXPORT(void,png_save_uint_16)
 
 /* Variables declared in png.c - only it needs to define PNG_NO_EXTERN */
 #if !defined(PNG_NO_EXTERN) || defined(PNG_ALWAYS_EXTERN)
-/* place to hold the signature string for a PNG file. */
+/* Place to hold the signature string for a PNG file. */
 #ifdef PNG_USE_GLOBAL_ARRAYS
    PNG_EXPORT_VAR (PNG_CONST png_byte FARDATA) png_sig[8];
 #else
diff --git a/pngwutil.c b/pngwutil.c
index 25df2e2d..cabcb338 100644
--- a/pngwutil.c
+++ b/pngwutil.c
@@ -1,7 +1,7 @@
 
 /* pngwutil.c - utilities to write a PNG file
  *
- * Last changed in libpng 1.2.39 [August 13, 2009]
+ * Last changed in libpng 1.2.40 [August 19, 2009]
  * Copyright (c) 1998-2009 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.)
@@ -102,6 +102,7 @@ png_write_chunk_start(png_structp png_ptr, png_bytep chunk_name,
 
    png_debug2(0, "Writing %s chunk, length = %lu", chunk_name,
       (unsigned long)length);
+
    if (png_ptr == NULL)
       return;