diff --git a/sbin/ipfw/Makefile b/sbin/ipfw/Makefile
index 552755a1696..237a4a0007d 100644
--- a/sbin/ipfw/Makefile
+++ b/sbin/ipfw/Makefile
@@ -6,6 +6,7 @@ PACKAGE=ipfw
 PROG=	ipfw
 SRCS=	ipfw2.c dummynet.c ipv6.c main.c nat.c tables.c
 SRCS+=	nat64clat.c nat64lsn.c nat64stl.c nptv6.c
+SRCS+=	sync.c
 
 .if ${MK_PF} != "no"
 SRCS+=	altq.c