diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8bdb64e4..2ce5400c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -10,12 +10,13 @@ if(NANA_ENABLE_PNG)
 	add_definitions(-DNANA_ENABLE_PNG)
 endif()
 
-option(NANA_LIBPNG "Use the system installed libpng" OFF)
+option(NANA_LIBPNG "Use the included libpng" ON)
 if(NANA_LIBPNG)
+	add_definitions(-DNANA_LIBPNG)
+else()
 	find_package(PNG)
 	if (PNG_FOUND)
 		include_directories( ${PNG_INCLUDE_DIRS})
-		add_definitions(-DNANA_LIBPNG)
 	endif()
 endif()