diff --git a/ANNOUNCE b/ANNOUNCE
index 59d01d680..8f04cf2cb 100644
--- a/ANNOUNCE
+++ b/ANNOUNCE
@@ -1,5 +1,5 @@
 
-Libpng 1.6.0beta33 - December 9, 2012
+Libpng 1.6.0beta33 - December 10, 2012
 
 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.
@@ -552,9 +552,11 @@ Version 1.6.0beta32 [November 25, 2012]
   Fixed error checking in the simplified write API (Olaf van der Spek)
   Made png_user_version_check() ok to use with libpng version 1.10.x and later.
 
-Version 1.6.0beta33 [December 9, 2012]
+Version 1.6.0beta33 [December 10, 2012]
   Fixed typo in png.c (PNG_SET_CHUNK_MALLOC_MAX should be PNG_CHUNK_MALLOC_MAX)
     that causes the MALLOC_MAX limit not to work (John Bowler)
+  Change png_warning() to png_app_error() in pngwrite.c and comment the
+    fall-through condition.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
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diff --git a/CHANGES b/CHANGES
index 2c573e475..7a629d135 100644
--- a/CHANGES
+++ b/CHANGES
@@ -4304,9 +4304,11 @@ Version 1.6.0beta32 [November 25, 2012]
   Fixed error checking in the simplified write API (Olaf van der Spek)
   Made png_user_version_check() ok to use with libpng version 1.10.x and later.
 
-Version 1.6.0beta33 [December 9, 2012]
+Version 1.6.0beta33 [December 10, 2012]
   Fixed typo in png.c (PNG_SET_CHUNK_MALLOC_MAX should be PNG_CHUNK_MALLOC_MAX)
     that causes the MALLOC_MAX limit not to work (John Bowler)
+  Change png_warning() to png_app_error() in pngwrite.c and comment the
+    fall-through condition.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/pngwrite.c b/pngwrite.c
index 36886e07c..e0ca5f32b 100644
--- a/pngwrite.c
+++ b/pngwrite.c
@@ -936,7 +936,8 @@ png_set_filter(png_structrp png_ptr, int method, int filters)
 #ifdef PNG_WRITE_FILTER_SUPPORTED
          case 5:
          case 6:
-         case 7: png_warning(png_ptr, "Unknown row filter for method 0");
+         case 7: png_app_error(png_ptr, "Unknown row filter for method 0");
+            /* Fall through */
 #endif /* PNG_WRITE_FILTER_SUPPORTED */
          case PNG_FILTER_VALUE_NONE:
             png_ptr->do_filter = PNG_FILTER_NONE; break;
@@ -958,7 +959,7 @@ png_set_filter(png_structrp png_ptr, int method, int filters)
             png_ptr->do_filter = (png_byte)filters; break;
 #else
          default:
-            png_warning(png_ptr, "Unknown row filter for method 0");
+            png_app_error(png_ptr, "Unknown row filter for method 0");
 #endif /* PNG_WRITE_FILTER_SUPPORTED */
       }