diff --git a/CMakeLists.txt b/CMakeLists.txt
index aa4cc31..edcbe33 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -2,7 +2,12 @@ cmake_minimum_required(VERSION 3.11)
 
 project(tl-function_ref VERSION 1.0.0 LANGUAGES CXX)
 
-option(FUNCTION_REF_ENABLE_TESTS "Enable tests." ON)
+get_directory_property(is_subproject PARENT_DIRECTORY)
+if(NOT is_subproject)
+  set(is_mainproject YES)
+endif()
+
+option(FUNCTION_REF_ENABLE_TESTS "Enable tests." ${is_mainproject})
 
 include(FetchContent)
 FetchContent_Declare(
@@ -37,4 +42,4 @@ if(FUNCTION_REF_ENABLE_TESTS)
   target_link_libraries(tests Catch function-ref)
 
   set_property(TARGET tests PROPERTY CXX_STANDARD 14)
-endif()
\ No newline at end of file
+endif()