diff --git a/include/ruby/internal/config.h b/include/ruby/internal/config.h
index 51f863fc29..0c434e5b05 100644
--- a/include/ruby/internal/config.h
+++ b/include/ruby/internal/config.h
@@ -147,7 +147,7 @@
 #endif /* HAVE_VA_ARGS_MACRO */
 
 #ifndef USE_RVARGC
-# define USE_RVARGC 0
+# define USE_RVARGC 1
 #endif
 
 #endif /* RBIMPL_CONFIG_H */