diff --git a/CMakeLists.txt b/CMakeLists.txt
index aaf51b5..fa8e635 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -11,7 +11,6 @@ option(toml11_TEST_WITH_UBSAN "use LLVM undefined behavior sanitizer" OFF)
 option(TOML11_USE_UNRELEASED_TOML_FEATURES
     "use features in toml-lang/toml master while testing" OFF)
 
-include(CheckCXXCompilerFlag)
 set(CMAKE_CXX_EXTENSIONS OFF CACHE BOOL "Boolean specifying whether compiler specific extensions are requested.")
 if(NOT DEFINED CMAKE_CXX_STANDARD)
     message(FATAL_ERROR "CMAKE_CXX_STANDARD is not defined. \
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 332eaa8..8253359 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -55,6 +55,8 @@ set(TEST_NAMES
     test_extended_conversions
 )
 
+include(CheckCXXCompilerFlag)
+
 CHECK_CXX_COMPILER_FLAG("-Wall"      COMPILER_SUPPORTS_WALL)
 CHECK_CXX_COMPILER_FLAG("-Wextra"    COMPILER_SUPPORTS_WEXTRA)
 CHECK_CXX_COMPILER_FLAG("-Wpedantic" COMPILER_SUPPORTS_WPEDANTIC)