diff --git a/lib/libmilter/Makefile b/lib/libmilter/Makefile
index bf96cc778707..75c93333fc5d 100644
--- a/lib/libmilter/Makefile
+++ b/lib/libmilter/Makefile
@@ -8,6 +8,7 @@ SENDMAIL_DIR=${.CURDIR}/../../contrib/sendmail
 CFLAGS+=-I${SENDMAIL_DIR}/src -I${SENDMAIL_DIR}/include -I.
 CFLAGS+=-DNOT_SENDMAIL -Dsm_snprintf=snprintf
 CFLAGS+=-D_THREAD_SAFE
+CFLAGS+=-DSM_CONF_POLL
 
 .if ${MK_INET6_SUPPORT} != "no"
 CFLAGS+=-DNETINET6