diff -urN widelands.orig/src/machdep.h widelands/src/machdep.h
--- widelands.orig/src/machdep.h	2005-05-04 22:31:16.000000000 -0400
+++ widelands/src/machdep.h	2005-05-04 22:31:37.000000000 -0400
@@ -36,6 +36,10 @@
 #undef P_BIG_ENDIAN
 #define P_LITTLE_ENDIAN
 #undef P_ALIGNMENT
+#elif defined (__x86_64__)
+#undef P_BIG_ENDIAN
+#define P_LITTLE_ENDIAN
+#undef P_ALIGNMENT
 #else
 #error architecture not supported
 #endif