diff --git a/cmake/modules/RootBuildOptions.cmake b/cmake/modules/RootBuildOptions.cmake
index 07d21243e6dfc5a7b6ab5be919ece04b1adb3c04..4ea98db9d0d485bed868acbf94e665453cfd2dba 100644
--- a/cmake/modules/RootBuildOptions.cmake
+++ b/cmake/modules/RootBuildOptions.cmake
@@ -306,8 +306,11 @@ endif()
 ROOT_APPLY_OPTIONS()
 
 if(root7)
-  if(NOT CMAKE_CXX_STANDARD GREATER 11)
+  if(NOT CMAKE_CXX_STANDARD)
       set(CMAKE_CXX_STANDARD 14 CACHE STRING "C++14 standard used with root7")
+  endif()
+  if(NOT CMAKE_CXX_STANDARD GREATER 11)
+      message(FATAL_ERROR ">>> C++14 standard required with root7")
    endif()
    if(NOT webui AND NOT webui_disabled)
       set(webui ON CACHE BOOL "(webui build automatically when root7 is enabled)" FORCE)