diff --git a/arch/sandbox/dts/Makefile b/arch/sandbox/dts/Makefile
index b6a8847..f810b47 100644
--- a/arch/sandbox/dts/Makefile
+++ b/arch/sandbox/dts/Makefile
@@ -18,4 +18,4 @@
 dtbs: $(addprefix $(obj)/, $(dtb-y))
 	@:
 
-clean-files := *.dtb
+clean-files := *.dtb *.dtbo