diff --git a/ANNOUNCE b/ANNOUNCE
index 03b29119c..da13b1796 100644
--- a/ANNOUNCE
+++ b/ANNOUNCE
@@ -1,5 +1,5 @@
 
-Libpng 1.5.24beta02 - August 19, 2015
+Libpng 1.5.24beta02 - August 21, 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.
@@ -43,7 +43,8 @@ Version 1.5.24beta01 [August 19, 2015]
     in ANSI-C (unlike 0x80000000 in the signed case) the checking that
     occurs later can catch them (John Bowler).
 
-Version 1.5.24beta02 [August 19, 2015]
+Version 1.5.24beta02 [August 21, 2015]
+  Fixed png_save_int_32 when int is not 2's complement (John Bowler).
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/CHANGES b/CHANGES
index 6bc84a7c8..c530ba9f3 100644
--- a/CHANGES
+++ b/CHANGES
@@ -4389,7 +4389,8 @@ Version 1.5.24beta01 [August 19, 2015]
     in ANSI-C (unlike 0x80000000 in the signed case) the checking that
     occurs later can catch them (John Bowler).
 
-Version 1.5.24beta02 [August 19, 2015]
+Version 1.5.24beta02 [August 21, 2015]
+  Fixed png_save_int_32 when int is not 2's complement (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 04883d43e..fc028637a 100644
--- a/pngwutil.c
+++ b/pngwutil.c
@@ -30,19 +30,20 @@ png_save_uint_32(png_bytep buf, png_uint_32 i)
 }
 
 #ifdef PNG_SAVE_INT_32_SUPPORTED
-/* The png_save_int_32 function assumes integers are stored in two's
- * complement format.  If this isn't the case, then this routine needs to
- * be modified to write data in two's complement format.  Note that,
- * the following works correctly even if png_int_32 has more than 32 bits
- * (compare the more complex code required on read for sign extention.)
+/* PNG signed integers are saved in 32-bit 2's complement format.  ANSI C-90
+ * defines a cast of a signed integer to an unsigned integer either to preserve
+ * the value, if it is positive, or to calculate:
+ *
+ *     (UNSIGNED_MAX+1) + integer
+ *
+ * Where UNSIGNED_MAX is the appropriate maximum unsigned value, so when the
+ * negative integral value is added the result will be an unsigned value
+ * correspnding to the 2's complement representation.
  */
 void PNGAPI
 png_save_int_32(png_bytep buf, png_int_32 i)
 {
-   buf[0] = (png_byte)((i >> 24) & 0xff);
-   buf[1] = (png_byte)((i >> 16) & 0xff);
-   buf[2] = (png_byte)((i >> 8) & 0xff);
-   buf[3] = (png_byte)(i & 0xff);
+   png_save_uint_32(buf, i);
 }
 #endif