diff --git a/dtool/CompilerFlags.cmake b/dtool/CompilerFlags.cmake
index 8f52bed3a3..c38eafecc2 100644
--- a/dtool/CompilerFlags.cmake
+++ b/dtool/CompilerFlags.cmake
@@ -33,6 +33,7 @@ if(CMAKE_VERSION VERSION_LESS "3.1")
 
 else()
   set(CMAKE_CXX_STANDARD 11)
+  set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
 endif()