diff --git a/cmake/system.cmake b/cmake/system.cmake
index 3ca06665ab2385e34302a6bcce7ada549ea1e247..75a9d8fc25674e1dd0f5b73cd0ccde48204f63aa 100644
--- a/cmake/system.cmake
+++ b/cmake/system.cmake
@@ -28,6 +28,11 @@ ELSE(WIN32)
         STRING(REGEX MATCH "[0-9]+.[0-9]+" VERSION "${MACOSX_VERSION}")
         SET(MACOS_VERSION ${VERSION})
         SET(HOST_SYSTEM "macosx")
+        IF(NOT DEFINED ENV{MACOSX_DEPLOYMENT_TARGET})
+            # Set cache variable - end user may change this during ccmake or cmake-gui configure.
+            SET(CMAKE_OSX_DEPLOYMENT_TARGET ${MACOS_VERSION} CACHE STRING
+                "Minimum OS X version to target for deployment (at runtime); newer APIs weak linked. Set to empty string for default value.")
+        ENDIF()
     ELSE(APPLE)
 
         IF(EXISTS "/etc/issue")