diff --git a/ANNOUNCE b/ANNOUNCE
index f93ac58ff..30de9f551 100644
--- a/ANNOUNCE
+++ b/ANNOUNCE
@@ -1,4 +1,4 @@
-Libpng 1.6.19beta04 - September 27, 2015
+Libpng 1.6.19beta04 - October 3, 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.
@@ -92,10 +92,15 @@ Version 1.6.19beta03 [September 26, 2015]
     warning, updated pngstest-errors.h for the errors detected with the
     new contrib/testspngs PNG test files (John Bowler).
 
-Version 1.6.19beta04 [September 27, 2015]
+Version 1.6.19beta04 [October 3, 2015]
   Worked around rgb-to-gray issues in libpng 1.6.  The previous
     attempts to ignore the errors in the code aren't quite enough to
     deal with the 'channel selection' encoding added to libpng 1.7; abort.
+  Fixed 'pow' macros in pngvalid.c. It is legal for 'pow' to be a
+    macro, therefore the argument list cannot contain preprocessing
+    directives.  Make sure pow is a function where this happens. This is
+    a minimal safe fix, the issue only arises in non-performance-critical
+    code (bug report by Curtis Leach, fix by John Bowler).
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/CHANGES b/CHANGES
index 09221b3d5..5f339df24 100644
--- a/CHANGES
+++ b/CHANGES
@@ -5375,11 +5375,16 @@ Version 1.6.19beta03 [September 26, 2015]
     warning, updated pngstest-errors.h for the errors detected with the
     new contrib/testspngs PNG test files (John Bowler).
 
-Version 1.6.19beta04 [September 27, 2015]
+Version 1.6.19beta04 [October 3, 2015]
   Worked around rgb-to-gray issues in libpng 1.6.  The previous
     attempts to ignore the errors in the code aren't quite enough to
     deal with the 'channel selection' encoding added to libpng 1.7; abort.
     pngvalid.c is changed to drop this encoding in prior versions.
+  Fixed 'pow' macros in pngvalid.c. It is legal for 'pow' to be a
+    macro, therefore the argument list cannot contain preprocessing
+    directives.  Make sure pow is a function where this happens. This is
+    a minimal safe fix, the issue only arises in non-performance-critical
+    code (bug report by Curtis Leach, fix by John Bowler).
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit