diff --git a/client_server/CMakeLists.txt b/client_server/CMakeLists.txt
index 080dc6b102..9af29df845 100644
--- a/client_server/CMakeLists.txt
+++ b/client_server/CMakeLists.txt
@@ -106,7 +106,6 @@ add_definitions(
    -DBOOST_BIND_GLOBAL_PLACEHOLDERS
    -DBOOST_ASIO_USE_TS_EXECUTOR_AS_DEFAULT
    -DASIO_STANDALONE
-   -D_WEBSOCKETPP_CPP11_INTERNAL_
  )
 
 #---------------------------------------------------------------------------