diff --git a/doomsday/cmake/PlatformMacx.cmake b/doomsday/cmake/PlatformMacx.cmake
index 49f20d0de8..07add172d1 100644
--- a/doomsday/cmake/PlatformMacx.cmake
+++ b/doomsday/cmake/PlatformMacx.cmake
@@ -11,6 +11,15 @@ set (DENG_CODESIGN_APP_CERT "" CACHE STRING "ID of the certificate for signing a
 find_program (CODESIGN_COMMAND codesign)
 mark_as_advanced (CODESIGN_COMMAND)
 
+# Detect OS X version.
+execute_process (COMMAND sw_vers -productVersion 
+    OUTPUT_VARIABLE MACOS_VERSION 
+    OUTPUT_STRIP_TRAILING_WHITESPACE
+)
+
+if (NOT MACOS_VERSION VERSION_LESS 10.7)
+    add_definitions (-DMACOS_10_7)
+endif ()
 add_definitions (
     -DMACOSX
     # Fallback basedir for command line apps.