diff --git a/ANNOUNCE b/ANNOUNCE
index d3fd78005..559a2235a 100644
--- a/ANNOUNCE
+++ b/ANNOUNCE
@@ -1,4 +1,4 @@
-Libpng 1.6.26beta01 - September 12, 2016
+Libpng 1.6.26beta01 - September 19, 2016
 
 This is not intended to be a public release.  It will be replaced
 within a few weeks by a public version or by another test version.
@@ -25,7 +25,7 @@ Other information:
 
 Changes since the last public release (1.6.25):
 
-Version 1.6.26beta01 [September 12, 2016]
+Version 1.6.26beta01 [September 19, 2016]
   Fixed handling zero length IDAT in pngfix (bug report by Agostino Sarubbo,
     bugfix by John Bowler).
   Do not issue a png_error() on read in png_set_pCAL() because png_handle_pCAL
@@ -33,6 +33,8 @@ Version 1.6.26beta01 [September 12, 2016]
   Conditionally compile png_set_benign_errors() in pngread.c and pngtest.c
   Issue a png_benign_error instead of a png_error on ADLER32 mismatch
     while decoding compressed data chunks.
+  Changed PNG_ZLIB_VERNUM to ZLIB_VERNUM in pngpriv.h, pngstruct.h, and
+    pngrutil.c.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/CHANGES b/CHANGES
index 2b318c790..ff7143a6d 100644
--- a/CHANGES
+++ b/CHANGES
@@ -5703,7 +5703,7 @@ Version 1.6.25rc05 [August 30, 2016]
 Version 1.6.25 [September 1, 2016]
   No changes.
 
-Version 1.6.26beta01 [September 12, 2016]
+Version 1.6.26beta01 [September 19, 2016]
   Fixed handling zero length IDAT in pngfix (bug report by Agostino Sarubbo,
     bugfix by John Bowler).
   Do not issue a png_error() on read in png_set_pCAL() because png_handle_pCAL
@@ -5711,6 +5711,8 @@ Version 1.6.26beta01 [September 12, 2016]
   Conditionally compile png_set_benign_errors() in pngread.c and pngtest.c
   Issue a png_benign_error instead of a png_error on ADLER32 mismatch
     while decoding compressed data chunks.
+  Changed PNG_ZLIB_VERNUM to ZLIB_VERNUM in pngpriv.h, pngstruct.h, and
+    pngrutil.c.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/pngpriv.h b/pngpriv.h
index bed1cabe7..a71ea1610 100644
--- a/pngpriv.h
+++ b/pngpriv.h
@@ -1263,7 +1263,7 @@ PNG_INTERNAL_FUNCTION(void,png_read_finish_row,(png_structrp png_ptr),
 /* Initialize the row buffers, etc. */
 PNG_INTERNAL_FUNCTION(void,png_read_start_row,(png_structrp png_ptr),PNG_EMPTY);
 
-#if PNG_ZLIB_VERNUM >= 0x1240
+#if ZLIB_VERNUM >= 0x1240
 PNG_INTERNAL_FUNCTION(int,png_zlib_inflate,(png_structrp png_ptr, int flush),
       PNG_EMPTY);
 #  define PNG_INFLATE(pp, flush) png_zlib_inflate(pp, flush)
diff --git a/pngrutil.c b/pngrutil.c
index c619cbb5e..26a8ebc99 100644
--- a/pngrutil.c
+++ b/pngrutil.c
@@ -370,7 +370,7 @@ png_inflate_claim(png_structrp png_ptr, png_uint_32 owner)
     */
    {
       int ret; /* zlib return code */
-#if PNG_ZLIB_VERNUM >= 0x1240
+#if ZLIB_VERNUM >= 0x1240
 
 # if defined(PNG_SET_OPTION_SUPPORTED) && defined(PNG_MAXIMUM_INFLATE_WINDOW)
       int window_bits;
@@ -402,7 +402,7 @@ png_inflate_claim(png_structrp png_ptr, png_uint_32 owner)
 
       if ((png_ptr->flags & PNG_FLAG_ZSTREAM_INITIALIZED) != 0)
       {
-#if PNG_ZLIB_VERNUM < 0x1240
+#if ZLIB_VERNUM < 0x1240
          ret = inflateReset(&png_ptr->zstream);
 #else
          ret = inflateReset2(&png_ptr->zstream, window_bits);
@@ -411,7 +411,7 @@ png_inflate_claim(png_structrp png_ptr, png_uint_32 owner)
 
       else
       {
-#if PNG_ZLIB_VERNUM < 0x1240
+#if ZLIB_VERNUM < 0x1240
          ret = inflateInit(&png_ptr->zstream);
 #else
          ret = inflateInit2(&png_ptr->zstream, window_bits);
@@ -435,7 +435,7 @@ png_inflate_claim(png_structrp png_ptr, png_uint_32 owner)
 #endif
 }
 
-#if PNG_ZLIB_VERNUM >= 0x1240
+#if ZLIB_VERNUM >= 0x1240
 /* Handle the start of the inflate stream if we called inflateInit2(strm,0);
  * in this case some zlib versions skip validation of the CINFO field and, in
  * certain circumstances, libpng may end up displaying an invalid image, in
@@ -4103,7 +4103,7 @@ png_read_IDAT_data(png_structrp png_ptr, png_bytep output,
          if (output != NULL)
          {
             if(!strncmp(png_ptr->zstream.msg,"incorrect data check",20))
-               png_chunk_benign_error(png_ptr, png_ptr->zstream.msg);
+               png_chunk_benign_error(png_ptr, "ADLER32 checksum mismatch");
             else
                png_chunk_error(png_ptr, png_ptr->zstream.msg);
          }
diff --git a/pngstruct.h b/pngstruct.h
index 2b0eb4902..55516eaaa 100644
--- a/pngstruct.h
+++ b/pngstruct.h
@@ -263,7 +263,7 @@ struct png_struct_def
                               /* pixel depth used for the row buffers */
    png_byte transformed_pixel_depth;
                               /* pixel depth after read/write transforms */
-#if PNG_ZLIB_VERNUM >= 0x1240
+#if ZLIB_VERNUM >= 0x1240
    png_byte zstream_start;    /* at start of an input zlib stream */
 #endif /* Zlib >= 1.2.4 */
 #if defined(PNG_READ_FILLER_SUPPORTED) || defined(PNG_WRITE_FILLER_SUPPORTED)