diff --git a/version.h b/version.h
index a1b48bef90..50ace17e94 100644
--- a/version.h
+++ b/version.h
@@ -15,7 +15,7 @@
 
 #define RUBY_RELEASE_YEAR 2021
 #define RUBY_RELEASE_MONTH 9
-#define RUBY_RELEASE_DAY 20
+#define RUBY_RELEASE_DAY 21
 
 #include "ruby/version.h"