diff --git a/CMake/BoostConfig.cmake b/CMake/BoostConfig.cmake
index 1b2aef80e..ada1888da 100644
--- a/CMake/BoostConfig.cmake
+++ b/CMake/BoostConfig.cmake
@@ -102,7 +102,7 @@ message(STATUS "Boost compiler: ${BOOST_COMPILER}")
 message(STATUS "Boost toolset:  ${BOOST_TOOLSET}")
 
 # create cache entry
-set(BOOST_PLATFORM "unknown" CACHE STRING "Boost platform name")
+set(BOOST_PLATFORM "unknown")
 
 # Multi-threading support
 if(CMAKE_SYSTEM_NAME STREQUAL "SunOS")
@@ -150,6 +150,9 @@ else()
   set(BOOST_PLATFORM "unknown")
 endif()
 
+# create cache entry
+set(BOOST_PLATFORM ${BOOST_PLATFORM} CACHE STRING "Boost platform name")
+
 message(STATUS "Boost platform: ${BOOST_PLATFORM}")
 
 # Setup DEBUG_COMPILE_FLAGS, RELEASE_COMPILE_FLAGS, DEBUG_LINK_FLAGS and