diff -ur a/CMakeLists.txt b/CMakeLists.txt
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -136,7 +136,7 @@
 # other subdirectories
 # only add if not inside add_subdirectory()
 option(TYPE_SAFE_BUILD_TEST_EXAMPLE "build test and example" OFF)
-if(${TYPE_SAFE_BUILD_TEST_EXAMPLE} OR (CMAKE_CURRENT_SOURCE_DIR STREQUAL CMAKE_SOURCE_DIR))
+if(${TYPE_SAFE_BUILD_TEST_EXAMPLE})
     enable_testing()
     add_subdirectory(example/)
     add_subdirectory(test/)