diff --git a/include/mrbconf.h b/include/mrbconf.h
index f496c53d9..4ed481e0b 100644
--- a/include/mrbconf.h
+++ b/include/mrbconf.h
@@ -11,7 +11,7 @@
 
 /* configuration options: */
 /* add -DMRB_USE_FLOAT to use float instead of double for floating point numbers */
-#undef MRB_USE_FLOAT
+//#define MRB_USE_FLOAT
 
 /* -DDISABLE_XXXX to change to drop the feature */
 #define DISABLE_REGEXP	        /* regular expression classes */