diff --git a/CMakeLists.txt b/CMakeLists.txt
index aed9ac8af..a7b9e8186 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,4 +1,13 @@
-CMAKE_MINIMUM_REQUIRED(VERSION 2.4.6 FATAL_ERROR)
+IF(WIN32)
+    CMAKE_MINIMUM_REQUIRED(VERSION 2.4.6 FATAL_ERROR)
+ELSE(WIN32)
+    IF(APPLE)
+        CMAKE_MINIMUM_REQUIRED(VERSION 2.4.6 FATAL_ERROR)
+    ELSE(APPLE)
+        CMAKE_MINIMUM_REQUIRED(VERSION 2.4.0 FATAL_ERROR)
+    ENDIF(APPLE)
+ENDIF(WIN32)
+
 
 PROJECT(OpenSceneGraph)