Index: trunk/FACT++/CMakeLists.txt
===================================================================
--- trunk/FACT++/CMakeLists.txt	(revision 19835)
+++ trunk/FACT++/CMakeLists.txt	(revision 19836)
@@ -277,4 +277,19 @@
       SET(CMAKE_Fortran_FLAGS "${CMAKE_Fortran_FLAGS} ${ROOT_fortran_FLAGS}")
    ENDIF()
+
+   IF(ROOTSYS AND NOT ROOTSYS STREQUAL $ENV{ROOTSYS})
+      MESSAGE(WARNING
+         " \n"
+         " ROOT Version changed!\n"
+         " Present  ROOTSYS: $ENV{ROOTSYS}\n"
+         " Previous ROOTSYS: ${ROOTSYS}")
+      FILE(REMOVE thisroot.sh)
+   ENDIF()
+
+   SET(ROOTSYS $ENV{ROOTSYS} CACHE INTERNAL "Internal variable to check for consistency in ROOTSYS")
+
+   # For convenience and easy tracking
+   ADD_CUSTOM_COMMAND(OUTPUT thisroot.sh COMMAND ln -sf ${ROOTSYS}/bin/thisroot.sh VERBATIM)
+   ADD_CUSTOM_TARGET(thisroot ALL DEPENDS thisroot.sh)
 
 ENDIF(NOT NO_ROOT AND NOT VIEWER_ONLY)