diff --git a/extern/CMakeProject-lua.cmake b/extern/CMakeProject-lua.cmake
index 70d45a95c7..a9482812cd 100644
--- a/extern/CMakeProject-lua.cmake
+++ b/extern/CMakeProject-lua.cmake
@@ -64,7 +64,7 @@ set_property(TARGET "lua-5.1" PROPERTY FOLDER "External Libraries")
 
 if(MSVC)
   sm_add_compile_definition("lua-5.1" _CRT_SECURE_NO_WARNINGS)
-  sm_add_compile_flag("lua-5.1" /TP)
+  set_source_files_properties(${LUA_SRC} PROPERTIES LANGUAGE CXX)
 endif(MSVC)
 
 disable_project_warnings("lua-5.1")