diff --git a/lib/libmilter/Makefile b/lib/libmilter/Makefile
index b3243c2a66cf..6f18d86b8385 100644
--- a/lib/libmilter/Makefile
+++ b/lib/libmilter/Makefile
@@ -40,3 +40,5 @@ sm_os.h: ${SENDMAIL_DIR}/include/sm/os/sm_os_freebsd.h .NOMETA
 	ln -sf ${.ALLSRC} ${.TARGET}
 
 .include <bsd.lib.mk>
+
+CWARNFLAGS+= ${NO_WDEPRECATED_NON_PROTOTYPE}