diff --git a/core/main.mk b/core/main.mk
index 2bd3163..d9ff68e 100644
--- a/core/main.mk
+++ b/core/main.mk
@@ -113,6 +113,11 @@
 $(shell rm -f $(OUT_DIR)/ninja_build)
 endif
 
+# With these files findleaves.py won't be unnecessarily slower even if
+# there is a user creates a copy of $(OUT_DIR).
+$(shell echo '# This file prevents findleaves.py from traversing this directory further' > $(OUT_DIR)/Android.mk)
+$(shell echo '# This file prevents findleaves.py from traversing this directory further' > $(OUT_DIR)/CleanSpec.mk)
+
 # Write the build number to a file so it can be read back in
 # without changing the command line every time.  Avoids rebuilds
 # when using ninja.