--- iptables-1.4.0/include/xtables.h
+++ iptables-1.4.0/include/xtables.h
@@ -219,6 +219,9 @@ enum exittype {
 };
 
 /* this is a special 64bit data type that is 8-byte aligned */
+#ifdef aligned_u64
+# undef aligned_u64
+#endif
 #define aligned_u64 u_int64_t __attribute__((aligned(8)))
 
 int check_inverse(const char option[], int *invert, int *optind, int argc);