diff --git a/build/cxx_flags.cmake b/build/cxx_flags.cmake
index 8cb9bd0..9e96889 100644
--- a/build/cxx_flags.cmake
+++ b/build/cxx_flags.cmake
@@ -42,14 +42,14 @@ function (require_cxx_flag cxx_flag)
   string(FIND "${CMAKE_CXX_FLAGS}" "${cxx_flag}" CXX_FLAG_FOUND)
 
   if (${CXX_FLAG_FOUND} EQUAL -1)
-    unset(LIBWEBM_HAVE_CXX_FLAG)
+    unset(LIBWEBM_HAVE_CXX_FLAG CACHE)
     message("Checking CXX compiler flag support for: " ${cxx_flag})
     check_cxx_compiler_flag("${cxx_flag}" LIBWEBM_HAVE_CXX_FLAG)
     if (NOT LIBWEBM_HAVE_CXX_FLAG)
       message(FATAL_ERROR
-              "${PROJECT_NAME} requires support for CXX flag: ${flag}.")
+              "${PROJECT_NAME} requires support for CXX flag: ${cxx_flag}.")
     endif ()
-    set(CMAKE_CXX_FLAGS "-std=c++11 ${CMAKE_CXX_FLAGS}" CACHE STRING "" FORCE)
+    set(CMAKE_CXX_FLAGS "${cxx_flag} ${CMAKE_CXX_FLAGS}" CACHE STRING "" FORCE)
   endif ()
 endfunction ()