diff --git a/usr.sbin/tcpdchk/Makefile b/usr.sbin/tcpdchk/Makefile
index fa33290e582d..3c5a040ed8cf 100644
--- a/usr.sbin/tcpdchk/Makefile
+++ b/usr.sbin/tcpdchk/Makefile
@@ -8,7 +8,7 @@ PROG=	tcpdchk
 MAN=	tcpdchk.8
 SRCS=	tcpdchk.c fakelog.c inetcf.c scaffold.c
 
-CFLAGS=	-DREAL_DAEMON_DIR=\"/usr/libexec\" \
+CFLAGS+=-DREAL_DAEMON_DIR=\"/usr/libexec\" \
 	-DSEVERITY=LOG_INFO -DRFC931_TIMEOUT=10 \
 	-DHOSTS_DENY=\"/etc/hosts.deny\" -DHOSTS_ALLOW=\"/etc/hosts.allow\"
 .if !defined(NOINET6)