diff --git a/CMakeLists.txt b/CMakeLists.txt
index fa7de13a5..c01904417 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -43,7 +43,7 @@ if (${CMAKE_SYSTEM_NAME} MATCHES "Linux")
   set (LINUX true)
 elseif (${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
   set (DARWIN true)
-  set (CMAKE_CXX_FLAGS "-stdlib=libc++")
+  set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -stdlib=libc++")
 elseif (${CMAKE_SYSTEM_NAME} MATCHES "kFreeBSD")
   set (KFREEBSD true)
 elseif (${CMAKE_SYSTEM_NAME} MATCHES "FreeBSD")