diff --git a/ANNOUNCE b/ANNOUNCE
index 5ea1c12ab..15a731624 100644
--- a/ANNOUNCE
+++ b/ANNOUNCE
@@ -1,5 +1,5 @@
 
-Libpng 1.6.12rc02 - June 7, 2014
+Libpng 1.6.12rc02 - June 8, 2014
 
 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.
@@ -26,11 +26,15 @@ Other information:
 
 Changes since the last public release (1.6.11):
 
-Version 1.6.12rc01 [June 7, 2014]
+Version 1.6.12rc01 [June 6, 2014]
   Relocated new code from 1.6.11beta06 in png.c to a point after the
     declarations (Max Stepin).
+
+Version 1.6.12rc03 [June 8, 2014]
   Changed file permissions of contrib/tools/intgamma.sh,
     test-driver, and compile from 0644 to 0755 (Cosmin).
+  Ensure "__has_attribute()" macro exists before trying to use it with
+    old clang compilers (MacPorts Ticket #43939).
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/CHANGES b/CHANGES
index 16f5280ee..5a04d9f41 100644
--- a/CHANGES
+++ b/CHANGES
@@ -4925,11 +4925,15 @@ Version 1.6.11rc02 [June 3, 2014]
 Version 1.6.11 [June 5, 2014]
   No changes.
 
-Version 1.6.12rc01 [June 7, 2014]
+Version 1.6.12rc01 [June 6, 2014]
   Relocated new code from 1.6.11beta06 in png.c to a point after the
     declarations (Max Stepin).
+
+Version 1.6.12rc03 [June 8, 2014]
   Changed file permissions of contrib/tools/intgamma.sh,
     test-driver, and compile from 0644 to 0755 (Cosmin).
+  Ensure "__has_attribute()" macro exists before trying to use it with
+    old clang compilers (MacPorts Ticket #43939).
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/pngconf.h b/pngconf.h
index c524b7800..7211c8be9 100644
--- a/pngconf.h
+++ b/pngconf.h
@@ -1,7 +1,7 @@
 
 /* pngconf.h - machine configurable file for libpng
  *
- * libpng version 1.6.12rc02 - June 7, 2014
+ * libpng version 1.6.12rc02 - June 8, 2014
  *
  * Copyright (c) 1998-2014 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
@@ -361,7 +361,7 @@
    * version 1.2.41.  Disabling these removes the warnings but may also produce
    * less efficient code.
    */
-#  if defined(__clang__)
+#  if defined(__clang__) && defined(__has_attribute)
      /* Clang defines both __clang__ and __GNUC__. Check __clang__ first. */
 #    if !defined(PNG_USE_RESULT) && __has_attribute(__warn_unused_result__)
 #      define PNG_USE_RESULT __attribute__((__warn_unused_result__))