diff --git a/FindRAGEL.cmake b/FindRAGEL.cmake
index 192772e..5f7a166 100644
--- a/FindRAGEL.cmake
+++ b/FindRAGEL.cmake
@@ -43,6 +43,8 @@
 
 cmake_minimum_required(VERSION 3.14)
 
+include(CheckCXXCompilerFlag)
+
 find_program(RAGEL_EXECUTABLE NAMES ragel DOC "path to the ragel executable")
 mark_as_advanced(RAGEL_EXECUTABLE)