diff --git a/tools/building.py b/tools/building.py
index 57e58b9ab0894f80d5fd73997b3826abff5a06a8..ef1cb3da6689ac030c215fb409cafbc53f5aa160 100644
--- a/tools/building.py
+++ b/tools/building.py
@@ -286,8 +286,8 @@ def PrepareBuilding(env, root_directory, has_libcpu=False, remove_components = [
 
     # add program path
     env.PrependENVPath('PATH', rtconfig.EXEC_PATH)
-    # add rtconfig.h path
-    env.Append(CPPPATH = [str(Dir('#').abspath)])
+    # add rtconfig.h/BSP path into Kernel group
+    DefineGroup("Kernel", [], [], CPPPATH=[str(Dir('#').abspath)])
 
     # add library build action
     act = SCons.Action.Action(BuildLibInstallAction, 'Install compiled library... $TARGET')