diff --git a/ext/stringio/stringio.c b/ext/stringio/stringio.c
index c33464789c..7eade5bcba 100644
--- a/ext/stringio/stringio.c
+++ b/ext/stringio/stringio.c
@@ -13,7 +13,7 @@
 **********************************************************************/
 
 static const char *const
-STRINGIO_VERSION = "3.0.9";
+STRINGIO_VERSION = "3.1.0";
 
 #include "ruby.h"
 #include "ruby/io.h"