diff --git a/include/mruby/bigint.h b/include/mruby/bigint.h
index 364900ce9..643bc1204 100644
--- a/include/mruby/bigint.h
+++ b/include/mruby/bigint.h
@@ -31,7 +31,7 @@
 
 #include <sys/types.h>
 
-#ifdef MRB_32BIT
+#if !(defined(MRB_64BIT) || defined(MRB_INT64))
 /*
  * The values below are for 32 bit machines (i.e. machines with a
  *  32 bit long type)