diff --git a/CMakeLists.txt b/CMakeLists.txt
index 7c1d630..e5896a0 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -110,6 +110,10 @@ SET(LIBRARY_HEADERS
 	SDL2pp/Window.hh
 )
 
+SET(LIBRARY_EXTERNAL_HEADERS
+	SDL2pp/external/libcpp_optional.hh
+)
+
 IF(CMAKE_SOURCE_DIR STREQUAL PROJECT_SOURCE_DIR)
 	MESSAGE(STATUS "libSDL2pp standalone build")
 
@@ -151,6 +155,7 @@ IF(CMAKE_SOURCE_DIR STREQUAL PROJECT_SOURCE_DIR)
 
 	# install
 	INSTALL(FILES ${LIBRARY_HEADERS} ${PROJECT_BINARY_DIR}/SDL2pp/Config.hh DESTINATION include/SDL2pp)
+	INSTALL(FILES ${LIBRARY_EXTERNAL_HEADERS} DESTINATION include/SDL2pp/external)
 	INSTALL(TARGETS SDL2pp LIBRARY DESTINATION lib)
 	INSTALL(FILES ${PROJECT_BINARY_DIR}/sdl2pp.pc DESTINATION ${PKGCONFIGDIR})
 ELSE(CMAKE_SOURCE_DIR STREQUAL PROJECT_SOURCE_DIR)