diff --git a/share/mk/sys.mk b/share/mk/sys.mk
index 03e3d14a..5a598d6b 100644
--- a/share/mk/sys.mk
+++ b/share/mk/sys.mk
@@ -100,7 +100,7 @@ INSTALL=	${TOOLBINDIR}/binstall -U
 TAGSFILE=	tags
 
 #MANROFF=	nroff -man -h -Tascii
-MANROFF=	mandoc -Tascii
+MANROFF=	mandoc -Tascii -Ios="DiscoBSD ${OSREV}"
 
 ELF2AOUT=	${TOOLBINDIR}/elf2aout