diff --git a/parse.y b/parse.y
index c3a1bc5c43..e9252154e9 100644
--- a/parse.y
+++ b/parse.y
@@ -29,6 +29,8 @@
 # include RUBY_EXTCONF_H
 #endif
 
+#include "ruby/internal/config.h"
+
 #include <errno.h>
 #include "internal/ruby_parser.h"
 #include "parser_node.h"