diff --git a/ANNOUNCE b/ANNOUNCE
index 2f3cec2..11b301a 100644
--- a/ANNOUNCE
+++ b/ANNOUNCE
@@ -1,4 +1,4 @@
-Libpng 1.6.33beta01 - August 25, 2017
+Libpng 1.6.33beta01 - August 28, 2017
 
 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.
@@ -24,6 +24,8 @@
    libpng-1.6.33beta01-*.asc (armored detached GPG signatures)
 
 Changes since the last public release (1.6.32):
+  Added PNGMINUS_UNUSED macro to contrib/pngminus/p*.c and added missing
+    parenthesis in contrib/pngminus/pnm2png.c (bug report by Christian Hesse).
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/CHANGES b/CHANGES
index ad3a2fc..521d89d 100644
--- a/CHANGES
+++ b/CHANGES
@@ -5994,7 +5994,9 @@
 Version 1.6.32 [August 24, 2017]
   No changes.
 
-Version 1.6.33beta01 [August 25, 2017]
+Version 1.6.33beta01 [August 28, 2017]
+  Added PNGMINUS_UNUSED macro to contrib/pngminus/p*.c and added missing
+    parenthesis in contrib/pngminus/pnm2png.c (bug report by Christian Hesse).
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/contrib/pngminus/png2pnm.c b/contrib/pngminus/png2pnm.c
index 39a9f46..879db03 100644
--- a/contrib/pngminus/png2pnm.c
+++ b/contrib/pngminus/png2pnm.c
@@ -44,6 +44,7 @@
 #define PNG_DEBUG 0
 #endif
 
+
 #include "png.h"
 
 /* Define png_jmpbuf() in case we are using a pre-1.0.6 version of libpng */
@@ -51,6 +52,8 @@
 #  define png_jmpbuf(png_ptr) ((png_ptr)->jmpbuf)
 #endif
 
+#define PNGMINUS_UNUSED(param) (void)param;
+
 /* function prototypes */
 
 int  main (int argc, char *argv[]);
@@ -443,7 +446,7 @@
   if (png_pixels != (unsigned char*) NULL)
     free (png_pixels);
 
-  PNG_UNUSED(raw) /* to quiet a Coverity defect */
+  PNGMINUS_UNUSED(raw) /* to quiet a Coverity defect */
   return TRUE;
 
 } /* end of source */
diff --git a/contrib/pngminus/pnm2png.c b/contrib/pngminus/pnm2png.c
index 1b550b8..18f5bed 100644
--- a/contrib/pngminus/pnm2png.c
+++ b/contrib/pngminus/pnm2png.c
@@ -50,6 +50,8 @@
 #  define png_jmpbuf(png_ptr) ((png_ptr)->jmpbuf)
 #endif
 
+#define PNGMINUS_UNUSED(param) (void)param;
+
 /* function prototypes */
 
 int  main (int argc, char *argv[]);
@@ -376,7 +378,7 @@
   /* row_bytes is the width x number of channels x (bit-depth / 8) */
     row_bytes = width * channels * ((bit_depth <= 8) ? 1 : 2);
 
-  if ((row_bytes == 0 || (size_t)height > ((size_t)(-1))/(size_t)row_bytes)
+  if ((row_bytes == 0 || (size_t)height > ((size_t)(-1))/(size_t)row_bytes))
   {
     /* too big */ 
     return FALSE;
@@ -513,7 +515,7 @@
   if (png_pixels != (unsigned char*) NULL)
     free (png_pixels);
 
-  PNG_UNUSED(raw) /* Quiet a Coverity defect */
+  PNGMINUS_UNUSED(raw) /* Quiet a Coverity defect */
 
   return TRUE;
 } /* end of pnm2png */