diff --git a/CMakeLists.txt b/CMakeLists.txt
index 7090e19a..9af2d3a8 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -227,7 +227,7 @@ if(NANA_CMAKE_ENABLE_PNG)
     if(NANA_CMAKE_LIBPNG_FROM_OS)
         find_package(PNG)
         if (PNG_FOUND)
-            target_include_directories(${PROJECT_NAME} PRIVATE PNG::PNG)
+            target_include_directories(${PROJECT_NAME} SYSTEM PRIVATE PNG::PNG)
             target_compile_definitions(${PROJECT_NAME} PUBLIC USE_LIBPNG_FROM_OS)
         endif(PNG_FOUND)
     else()
@@ -241,12 +241,12 @@ if(NANA_CMAKE_ENABLE_JPEG)
     if(NANA_CMAKE_LIBJPEG_FROM_OS)
         find_package(JPEG)
         if (JPEG_FOUND)
-            target_include_directories(${PROJECT_NAME PRIVATE ${JPEG_INCLUDE_DIR})
+            target_include_directories(${PROJECT_NAME SYSTEM PRIVATE ${JPEG_INCLUDE_DIR})
             target_link_libraries(${PROJECT_NAME} PRIVATE ${JPEG_LIBRARIES})
             target_compile_definitions(${PROJECT_NAME} PUBLIC USE_LIBJPEG_FROM_OS)
         endif(JPEG_FOUND)
     else()
-        add_definitions(-DNANA_ENABLE_JPEG)
+        target_compile_definitions(${PROJECT_NAME} PUBLIC NANA_ENABLE_JPEG)
     endif(NANA_CMAKE_LIBJPEG_FROM_OS)
 endif(NANA_CMAKE_ENABLE_JPEG)