diff --git a/lib/libmilter/Makefile b/lib/libmilter/Makefile
index 17bb09857fc..b3243c2a66c 100644
--- a/lib/libmilter/Makefile
+++ b/lib/libmilter/Makefile
@@ -15,6 +15,11 @@ CFLAGS+=-DSM_CONF_POLL
 CFLAGS+=-DNETINET6
 .endif
 
+.if ${MK_OPENSSL} != "no"
+# STARTTLS support
+CFLAGS+=-DSTARTTLS
+.endif
+
 # User customizations to the sendmail build environment
 CFLAGS+=${SENDMAIL_CFLAGS}
 
diff --git a/lib/libsmutil/Makefile b/lib/libsmutil/Makefile
index ff3f8491225..7bbd21e21bb 100644
--- a/lib/libsmutil/Makefile
+++ b/lib/libsmutil/Makefile
@@ -1,5 +1,7 @@
 # $FreeBSD$
 
+.include <src.opts.mk>
+
 PACKAGE=lib${LIB}
 SENDMAIL_DIR=${SRCTOP}/contrib/sendmail
 .PATH:	${SENDMAIL_DIR}/libsmutil
@@ -7,6 +9,11 @@ SENDMAIL_DIR=${SRCTOP}/contrib/sendmail
 CFLAGS+=-I${SENDMAIL_DIR}/src -I${SENDMAIL_DIR}/include -I.
 CFLAGS+=-DNEWDB -DNIS -DMAP_REGEX -DNOT_SENDMAIL
 
+.if ${MK_OPENSSL} != "no"
+# STARTTLS support
+CFLAGS+=-DSTARTTLS
+.endif
+
 # User customizations to the sendmail build environment
 CFLAGS+=${SENDMAIL_CFLAGS}