diff --git a/ANNOUNCE b/ANNOUNCE
index 12ef92340..283d60c4f 100644
--- a/ANNOUNCE
+++ b/ANNOUNCE
@@ -1,5 +1,5 @@
 
-Libpng 1.7.0beta84 - August 18, 2016
+Libpng 1.7.0beta84 - September 1, 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.
@@ -1396,8 +1396,11 @@ Version 1.7.0beta83 [July 23, 2016]
     in reading.
   Fixed debug test of output gamma.
 
-Version 1.7.0beta84 [August 18, 2016]
+Version 1.7.0beta84 [September 1, 2016]
   Minor editing of INSTALL, (whitespace, added copyright line)
+  Don't install pngcp; it conflicts with pngcp in the pngtools package.
+  Fixed handling zero length IDAT in pngfix (bug report by Agostino Sarubbo,
+    bugfix by John Bowler).
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/CHANGES b/CHANGES
index ee7c832a2..e8a3ddbd0 100644
--- a/CHANGES
+++ b/CHANGES
@@ -5696,8 +5696,11 @@ Version 1.7.0beta83 [July 23, 2016]
     in reading.
   Fixed debug test of output gamma.
 
-Version 1.7.0beta84 [August 18, 2016]
+Version 1.7.0beta84 [September 1, 2016]
   Minor editing of INSTALL, (whitespace, added copyright line)
+  Don't install pngcp; it conflicts with pngcp in the pngtools package.
+  Fixed handling zero length IDAT in pngfix (bug report by Agostino Sarubbo,
+    bugfix by John Bowler).
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/contrib/tools/pngfix.c b/contrib/tools/pngfix.c
index b2043e3fb..fef10969d 100644
--- a/contrib/tools/pngfix.c
+++ b/contrib/tools/pngfix.c
@@ -2,7 +2,7 @@
  *
  * Copyright (c) 2014-2016 John Cunningham Bowler
  *
- * Last changed in libpng 1.6.21 [January 15, 2016]
+ * Last changed in libpng 1.6.26 [(PENDING RELEASE)]
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
@@ -1824,7 +1824,7 @@ IDAT_init(struct IDAT * const idat, struct file * const file)
 }
 
 static png_uint_32
-rechunk_length(struct IDAT *idat)
+rechunk_length(struct IDAT *idat, int start)
    /* Return the length for the next IDAT chunk, taking into account
     * rechunking.
     */
@@ -1836,7 +1836,7 @@ rechunk_length(struct IDAT *idat)
       const struct IDAT_list *cur;
       unsigned int count;
 
-      if (idat->idat_index == 0) /* at the new chunk (first time) */
+      if (start)
          return idat->idat_length; /* use the cache */
 
       /* Otherwise rechunk_length is called at the end of a chunk for the length
@@ -1995,7 +1995,7 @@ process_IDAT(struct file *file)
       idat->idat_index = 0; /* Index into chunk data */
 
       /* Update the chunk length to the correct value for the IDAT chunk: */
-      file->chunk->chunk_length = rechunk_length(idat);
+      file->chunk->chunk_length = rechunk_length(idat, 1/*start*/);
 
       /* Change the state to writing IDAT chunks */
       file->state = STATE_IDAT;
@@ -3473,7 +3473,8 @@ read_callback(png_structp png_ptr, png_bytep buffer, size_t count)
                      /* Write another IDAT chunk.  Call rechunk_length to
                       * calculate the length required.
                       */
-                     length = chunk->chunk_length = rechunk_length(file->idat);
+                     length = chunk->chunk_length =
+                         rechunk_length(file->idat, 0/*end*/);
                      assert(type == png_IDAT);
                      file->write_count = 0; /* for the new chunk */
                      --(file->write_count); /* fake out the increment below */