diff --git a/configure.ac b/configure.ac
index 35e493f..c7012b7 100644
--- a/configure.ac
+++ b/configure.ac
@@ -18,7 +18,7 @@ m4_ifdef([AM_PROG_AR], [AM_PROG_AR])
 LT_INIT([disable-static])
 
 # http://www.gnu.org/software/libtool/manual/html_node/Updating-version-info.html
-AC_SUBST([LIBBLKMAKER_SO_VERSION], [4:1:4])
+AC_SUBST([LIBBLKMAKER_SO_VERSION], [4:2:4])
 AC_SUBST([LIBBLKMAKER_API_VERSION], [0.1])
 
 AC_CONFIG_FILES([Makefile