diff -Naur libpng-1.2.29.orig/configure.ac libpng-1.2.29/configure.ac
--- libpng-1.2.29.orig/configure.ac	2008-05-08 07:58:11.000000000 -0400
+++ libpng-1.2.29/configure.ac	2008-05-31 20:21:12.000000000 -0400
@@ -63,7 +63,8 @@
 AC_MSG_CHECKING(
   [if assembler code in pnggccrd.c can be compiled without PNG_NO_MMX_CODE])
 AC_TRY_COMPILE(
-  [#include "$srcdir/pnggccrd.c"],
+  [#define PNG_CONFIGURE_LIBPNG
+   #include "$srcdir/pnggccrd.c"],
   [return 0;],
   AC_MSG_RESULT(yes)
   LIBPNG_NO_MMX="",
diff -Naur libpng-1.2.29.orig/pngconf.h libpng-1.2.29/pngconf.h
--- libpng-1.2.29.orig/pngconf.h	2008-05-08 07:58:03.000000000 -0400
+++ libpng-1.2.29/pngconf.h	2008-05-31 20:21:12.000000000 -0400
@@ -35,6 +35,25 @@
 #ifdef HAVE_CONFIG_H
 #include "config.h"
 #endif
+#else
+/* pngconf.h is part of the exported API. When a libpng-using application
+   includes us, PNG_CONFIGURE_LIBPNG is of course not defined as we do not have
+   libpng's config.h available in this case. This means that we do not have the
+   defines added to config.h and the commandline by libpng's ./configure .
+   
+   For all defines from config.h not having them set is not a problem, however
+   ./configure also adds -DPNG_NO_ASSEMBLER_CODE to the CFLAGS when compiling
+   on a platform on which the MMX and SSE asm code in libpng is not supported.
+   
+   We do need this define as this define is used to determine whether or not
+   to define PNG_ASSEMBLER_CODE_SUPPORTED and other assembler related defines
+   and prototypes. PNG_ASSEMBLER_CODE_SUPPORTED in turn is used by applications
+   (ImageMagick for example) to determine whether or not they can use the asm
+   functions. Thus we need to define PNG_NO_ASSEMBLER_CODE here on platforms
+   on which the MMX and SSE asm code in libpng is not supported: */
+#ifndef __i386__ /* change this if MMX/SSE become supported on x86_64! */
+#define PNG_NO_ASSEMBLER_CODE
+#endif
 #endif
 
 /*