diff --git a/ANNOUNCE b/ANNOUNCE
index 4bf43ad36..6e82c9722 100644
--- a/ANNOUNCE
+++ b/ANNOUNCE
@@ -1,4 +1,4 @@
-Libpng 1.6.17rc04 - March 15, 2015
+Libpng 1.6.17rc04 - March 16, 2015
 
 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.
@@ -39,6 +39,8 @@ Version 1.6.17beta01 [January 29, 2015]
   Merged some parts of libpng-1.6.17beta01 and libpng-1.7.0beta47.
   Added #ifndef __COVERITY__ where needed in png.c, pngrutil.c and
     pngset.c to avoid warnings about dead code.
+  Added "& 0xff" to many instances of expressions that are typecast
+    to (png_byte), to avoid Coverity gripes.
 
 Version 1.6.17beta02 [February 7, 2015]
   Work around one more Coverity-scan dead-code warning.
@@ -77,9 +79,11 @@ Version 1.6.17rc03 [March 12, 2015]
   Updated CMakeLists.txt to add OSX framework, change YES/NO to ON/OFF
     for consistency, and remove some useless tests (Alexey Petruchik).
 
-Version 1.6.17rc04 [March 15, 2015]
+Version 1.6.17rc04 [March 16, 2015]
   Remove pnglibconf.h, pnglibconf.c, and pnglibconf.out instead of
     pnglibconf.* in "make clean" (Cosmin).
+  Fix bug in calculation of maxbits, in png_write_sBIT, introduced
+    in libpng-1.6.17beta01 (John Bowler).
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/CHANGES b/CHANGES
index eb7172ace..7c2560f3c 100644
--- a/CHANGES
+++ b/CHANGES
@@ -5140,6 +5140,8 @@ Version 1.6.17beta01 [January 29, 2015]
   Merged some parts of libpng-1.6.17beta01 and libpng-1.7.0beta47.
   Added #ifndef __COVERITY__ where needed in png.c, pngrutil.c and
     pngset.c to avoid warnings about dead code.
+  Added "& 0xff" to many instances of expressions that are typecast
+    to (png_byte), to avoid Coverity gripes.
 
 Version 1.6.17beta02 [February 7, 2015]
   Work around one more Coverity-scan dead-code warning.
@@ -5178,9 +5180,11 @@ Version 1.6.17rc03 [March 12, 2015]
   Updated CMakeLists.txt to add OSX framework, change YES/NO to ON/OFF
     for consistency, and remove some useless tests (Alexey Petruchik).
 
-Version 1.6.17rc04 [March 15, 2015]
+Version 1.6.17rc04 [March 16, 2015]
   Remove pnglibconf.h, pnglibconf.c, and pnglibconf.out instead of
     pnglibconf.* in "make clean" (Cosmin).
+  Fix bug in calculation of maxbits, in png_write_sBIT, introduced
+    in libpng-1.6.17beta01 (John Bowler).
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/pngwutil.c b/pngwutil.c
index 3595944fe..3fe2ba791 100644
--- a/pngwutil.c
+++ b/pngwutil.c
@@ -1348,8 +1348,8 @@ png_write_sBIT(png_structrp png_ptr, png_const_color_8p sbit, int color_type)
    {
       png_byte maxbits;
 
-      maxbits = color_type==PNG_COLOR_TYPE_PALETTE ? 8 :
-         (png_byte)(png_ptr->usr_bit_depth & 0xff);
+      maxbits = (png_byte)((color_type==PNG_COLOR_TYPE_PALETTE ? 8 :
+          png_ptr->usr_bit_depth) & 0xff);
 
       if (sbit->red == 0 || sbit->red > maxbits ||
           sbit->green == 0 || sbit->green > maxbits ||