diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4fcbe8114..13a3626a4 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,6 +1,6 @@
 cmake_minimum_required(VERSION 3.12)
 
-project(SIRIUS VERSION 6.5.5)
+project(SIRIUS VERSION 6.5.6)
 
 # set language and standard
 enable_language(CXX Fortran)