diff --git a/src/OpenThreads/win32/CMakeLists.txt b/src/OpenThreads/win32/CMakeLists.txt
index 21fc70af7..84550bd7a 100644
--- a/src/OpenThreads/win32/CMakeLists.txt
+++ b/src/OpenThreads/win32/CMakeLists.txt
@@ -4,7 +4,9 @@ SET(LIB_NAME OpenThreads)
 SET(LIB_PUBLIC_HEADERS ${OpenThreads_PUBLIC_HEADERS})
 
 ADD_DEFINITIONS(-DWIN32_LEAN_AND_MEAN)
-ADD_DEFINITIONS(-D_WIN32_WINNT=0x0400)
+IF(NOT OSG_DETERMINE_WIN_VERSION)
+    ADD_DEFINITIONS(-D_WIN32_WINNT=0x0400)
+ENDIF(NOT OSG_DETERMINE_WIN_VERSION)
 SOURCE_GROUP("Header Files" FILES ${LIB_PUBLIC_HEADERS})
 SET_SOURCE_FILES_PROPERTIES(${LIB_PUBLIC_HEADERS} PROPERTIES HEADER_FILE_ONLY ON)