diff --git a/CMakeLists.txt b/CMakeLists.txt
index 20edcdc0..5d04d0c9 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -74,7 +74,7 @@ set(CMAKE_AUTOMOC ON)
 
 set(Grantlee5_MIN_PLUGIN_VERSION 0)
 
-set(Grantlee5_MAJOR_MINOR_VERSION_STRING "${Grantlee5_VERSION_MAJOR}.${Grantlee5_VERSION_MINOR}" )
+set(Grantlee5_MAJOR_MINOR_VERSION_STRING "${Grantlee5_VERSION_MAJOR}_${Grantlee5_VERSION_MINOR}" )
 
 set (LIB_SUFFIX "" CACHE STRING "Define suffix of library directory name (eg. '64')")