Index: open-invaders-0.3/headers/pmask.h
===================================================================
--- open-invaders-0.3.orig/headers/pmask.h	2014-10-16 22:10:56.948584921 +0800
+++ open-invaders-0.3/headers/pmask.h	2014-10-16 22:12:51.688587891 +0800
@@ -36,7 +36,12 @@
 //e.g. 4 for 16-bit ints, 5 for 32-bit ints, 6 for 64-bit ints
 //don't worry about setting it incorrectly
 //you'll get a compile error if you do, not a run-time error
-#define MASK_WORD_BITBITS 5
+#if defined(__alpha__) || defined(__ia64__) || (defined(__x86_64__) && defined(__LP64__)) || defined(__s390x__) || (defined(__sparc__) && defined(__arch64__)) \
+      || defined(__powerpc64__) || defined(__aarch64__) || (defined(__mips64) && defined(__LP64__))
+	#define MASK_WORD_BITBITS 6
+#else
+	#define MASK_WORD_BITBITS 5
+#endif
 
 
 //if SINGLE_MEMORY_BLOCK is defined