diff --git a/ch3/os/Makefile b/ch3/os/Makefile
index 5ed77c9..0c03143 100644
--- a/ch3/os/Makefile
+++ b/ch3/os/Makefile
@@ -44,7 +44,7 @@ run:build_elf $(KERNEL_BIN) $(SYMBOL_MAP) kill
 		-device loader,file=$(KERNEL_BIN),addr=$(KERNEL_ENTRY)
 
 clean:
-	#rm -rf ./target* && rm -rf ./src/link_app.S
+	rm -rf ./target* && rm -rf ./src/link_app.S
 
 kill:
 	-kill -9 $(QEMU_PID)