diff --git a/CMakeLists.txt b/CMakeLists.txt
index dfc39b8..8d8f0d6 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -16,4 +16,5 @@ add_executable(hello src/main.cpp src/null.cpp src/constexp.cpp)
 
 target_compile_features(hello PUBLIC cxx_std_20)
 
-target_include_directories(hello PRIVATE "${PROJECT_BINARY_DIR}/include")
+target_include_directories(hello PRIVATE "${PROJECT_BINARY_DIR}/include"
+                                         "${PROJECT_SOURCE_DIR}/include")
diff --git a/src/constexp.h b/include/constexp.h
similarity index 100%
rename from src/constexp.h
rename to include/constexp.h
diff --git a/src/null.h b/include/null.h
similarity index 100%
rename from src/null.h
rename to include/null.h