diff --git a/CMakeLists.txt b/CMakeLists.txt
index c631281fd..de312e6a2 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -15,7 +15,7 @@ set (PROJECT_VERSION "2.4.1")
 OPTION(USE_GNUTLS "Build gnutls support." ON)
 
 message ("CMAKE_SYSTEM_NAME ${CMAKE_SYSTEM_NAME}")
-set (CMAKE_CXX_FLAGS "-std=c++11")
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
 if (${CMAKE_SYSTEM_NAME} MATCHES "Linux")
   set (LINUX true)
 elseif (${CMAKE_SYSTEM_NAME} MATCHES "Darwin")