diff --git a/ChangeLog b/ChangeLog
index 3e6642a3..ae66e531 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2016-08-15 Even Rouault <even.rouault at spatialys.com>
+
+	* tools/tiff2bw.c: fix weight computation that could result of color
+	value overflow (no security implication). Fix bugzilla #2550.
+	Patch by Frank Freudenberg.
+
 2016-08-15 Even Rouault <even.rouault at spatialys.com>
 
 	* tools/rgb2ycbcr.c: validate values of -v and -h parameters to
diff --git a/tools/tiff2bw.c b/tools/tiff2bw.c
index 7464cf1e..743f455c 100644
--- a/tools/tiff2bw.c
+++ b/tools/tiff2bw.c
@@ -1,4 +1,4 @@
-/* $Id: tiff2bw.c,v 1.18 2015-06-21 01:09:10 bfriesen Exp $ */
+/* $Id: tiff2bw.c,v 1.19 2016-08-15 22:01:31 erouault Exp $ */
 
 /*
  * Copyright (c) 1988-1997 Sam Leffler
@@ -45,7 +45,7 @@
 #define	strneq(a,b,n)	(strncmp(a,b,n) == 0)
 
 /* x% weighting -> fraction of full color */
-#define	PCT(x)	(((x)*255+127)/100)
+#define	PCT(x)	(((x)*256+50)/100)
 int	RED = PCT(30);		/* 30% */
 int	GREEN = PCT(59);	/* 59% */
 int	BLUE = PCT(11);		/* 11% */