diff --git a/arch/sandbox/cpu/Makefile b/arch/sandbox/cpu/Makefile
index 2ae0f71..6fd09ff 100644
--- a/arch/sandbox/cpu/Makefile
+++ b/arch/sandbox/cpu/Makefile
@@ -27,7 +27,7 @@
 
 LIB	= $(obj)lib$(CPU).o
 
-COBJS	:= cpu.o start.o os.o
+COBJS	:= cpu.o os.o start.o state.o
 
 SRCS	:= $(COBJS:.o=.c)
 OBJS	:= $(addprefix $(obj),$(COBJS))