diff --git a/Modules/CMakeDetermineSystem.cmake b/Modules/CMakeDetermineSystem.cmake
index b826a7fa8..cfb28ead2 100644
--- a/Modules/CMakeDetermineSystem.cmake
+++ b/Modules/CMakeDetermineSystem.cmake
@@ -37,7 +37,7 @@ ELSE(UNIX)
   IF(WIN32)
     SET (CMAKE_SYSTEM_NAME "Windows")
     SET (CMAKE_SYSTEM_VERSION "")  
-    SET (CMAKE_SYSTEM_PROCESSOR "")
+    SET (CMAKE_SYSTEM_PROCESSOR "$ENV{PROCESSOR_ARCHITECTURE}")
   ENDIF(WIN32)
 ENDIF(UNIX)