diff --git a/security/heimdal/Makefile b/security/heimdal/Makefile
index 3508ad2f8f0c..dae850e063f3 100644
--- a/security/heimdal/Makefile
+++ b/security/heimdal/Makefile
@@ -45,7 +45,8 @@ CONFIGURE_ARGS=	--with-berkeley-db \
 		--sysconfdir="${PREFIX}/etc"
 # XXX --with-readline picks up libreadline even if found in /usr/lib.
 MAKE_ENV=	INSTALL_CATPAGES=no
-LDFLAGS=	-Wl,--undefined-version
+CFLAGS+=	-Wno-implicit-function-declaration
+LDFLAGS+=	-Wl,--undefined-version
 INSTALL_TARGET=	install-strip
 .if !exists(/etc/rc.d/ipropd_master)
 USE_RC_SUBR=	ipropd_master ipropd_slave