diff --git a/CMakeLists.txt b/CMakeLists.txt
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -86,9 +86,9 @@ else()
 endif()
 
 # version number
-set(MAJOR_VERSION 0)
-set(MINOR_VERSION 4)
-set(PATCH_VERSION 0)
+set(MAJOR_VERSION 0 CACHE INT "Program major version number.")
+set(MINOR_VERSION 4 CACHE INT "Program minor version number.")
+set(PATCH_VERSION 0 CACHE INT "Program patch version number.")
 set(VERSION_STRING "${MAJOR_VERSION}.${MINOR_VERSION}.${PATCH_VERSION}")
 
 # get revision number from mercurial