diff --git a/ANNOUNCE b/ANNOUNCE
index 83588bc54dd118b195f29c9e1b7118a774500b25..71699702c12c33714cb0d32730562f7b6ed8a902 100644
--- a/ANNOUNCE
+++ b/ANNOUNCE
@@ -1,5 +1,5 @@
 
-Libpng 1.6.4beta01 - July 21, 2013
+Libpng 1.6.4beta01 - August 21, 2013
 
 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.
@@ -26,7 +26,9 @@ Other information:
 
 Changes since the last public release (1.6.3):
 
-Version 1.6.4beta01 [July 21, 2013]
+Version 1.6.4beta01 [August 21, 2013]
+  Delay calling png_init_filter_functions() until a row with nonzero filter
+    is found.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/CHANGES b/CHANGES
index cd4934ea0cf92f9c80ca69dec3a8f96044f9b426..c21b2d7256bb38e4f8fe2602d768096973a03004 100644
--- a/CHANGES
+++ b/CHANGES
@@ -4618,7 +4618,9 @@ Version 1.6.3 [July 18, 2013]
   Added "/* SAFE */" comments in pngrutil.c and pngrtran.c where warnings
     may be erroneously issued by code-checking applications.
 
-Version 1.6.4beta01 [July 21, 2013]
+Version 1.6.4beta01 [August 21, 2013]
+  Delay calling png_init_filter_functions() until a row with nonzero filter
+    is found.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/pngrutil.c b/pngrutil.c
index 0a75cd81ce39889fb7c4a20390732e26b186d5ec..112c28f5fc64cfc881063dc369c6f9a4f5969c5f 100644
--- a/pngrutil.c
+++ b/pngrutil.c
@@ -1,7 +1,7 @@
 
 /* pngrutil.c - utilities to read a PNG file
  *
- * Last changed in libpng 1.6.3 [July 18, 2013]
+ * Last changed in libpng 1.6.4 [(PENDING RELEASE)]
  * Copyright (c) 1998-2013 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.)
@@ -3922,10 +3922,13 @@ png_read_filter_row(png_structrp pp, png_row_infop row_info, png_bytep row,
     * PNG_FILTER_OPTIMIZATIONS to a function that overrides the generic
     * implementations.  See png_init_filter_functions above.
     */
-   if (pp->read_filter[0] == NULL)
-      png_init_filter_functions(pp);
    if (filter > PNG_FILTER_VALUE_NONE && filter < PNG_FILTER_VALUE_LAST)
+   {
+      if (pp->read_filter[0] == NULL)
+         png_init_filter_functions(pp);
+
       pp->read_filter[filter-1](row_info, row, prev_row);
+   }
 }
 
 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED