Index: head/Mk/bsd.sanity.mk
===================================================================
--- head/Mk/bsd.sanity.mk
+++ head/Mk/bsd.sanity.mk
@@ -168,6 +168,14 @@
 .  endif
 .endfor
 
+.if empty(PORTEPOCH) || !empty(PORTEPOCH:C/[0-9]+//)
+DEV_ERROR+=	"PORTEPOCH needs to be an integer \>= 0"
+.endif
+
+.if empty(PORTREVISION) || !empty(PORTREVISION:C/[0-9]+//)
+DEV_ERROR+=	"PORTREVISION needs to be an integer \>= 0"
+.endif
+
 # Whitelist of options helper lookalikes that should not be reported on:
 _OPTIONS_HELPERS_SEEN+=	OPENSSL_LDFLAGS
 _BROKEN_OPTIONS_HELPERS=
Index: head/devel/elfio/Makefile
===================================================================
--- head/devel/elfio/Makefile
+++ head/devel/elfio/Makefile
@@ -3,7 +3,7 @@
 
 PORTNAME=	elfio
 PORTVERSION=	3.4
-PORTREVISION=
+PORTREVISION=	0
 CATEGORIES=	devel
 MASTER_SITES=	SF/elfio/ELFIO-sources/ELFIO-${PORTVERSION}
 
Index: head/devel/subversion/Makefile.addons
===================================================================
--- head/devel/subversion/Makefile.addons
+++ head/devel/subversion/Makefile.addons
@@ -12,7 +12,7 @@
 			${PORTNAME}-1.[^1][0-9].[0-9]* \
 			${PORTNAME}-1.1[0-1].[0-9]* \
 			${PORTNAME}-lts-1.[0-9][0-9].[0-9]*
-PORTREVISION=		${PORTREVISION_112}
+PORTREVISION=		${PORTREVISION_112:U0}
 PLIST_SUB+=		SVN112="" SVNLTS="@comment "
 LIB_DEPENDS+=		libsvn_client-1.so:devel/subversion
 OPTIONS_NAME=		devel_subversion
@@ -22,7 +22,7 @@
 PKGNAMESUFFIX:=		${PKGNAMESUFFIX}-lts
 CONFLICTS_BUILD+=	${PORTNAME}-1.[0-9].[0-9]* \
 			${PORTNAME}-1.[0-9][0-9].[0-9]*
-PORTREVISION=		${PORTREVISION_LTS}
+PORTREVISION=		${PORTREVISION_LTS:U0}
 PLIST_SUB+=		SVN112="@comment " SVNLTS=""
 LIB_DEPENDS+=		libsvn_client-1.so:devel/subversion-lts
 OPTIONS_NAME=		devel_subversion-lts
Index: head/games/xboard-devel/Makefile
===================================================================
--- head/games/xboard-devel/Makefile
+++ head/games/xboard-devel/Makefile
@@ -2,8 +2,8 @@
 
 PORTNAME=	xboard-devel
 PORTVERSION=	4.8.0.20151020.3
-PORTREVISION=
-PORTEPOCH=
+PORTREVISION=	0
+PORTEPOCH=	0
 MASTER_SITES=	http://freeheimdall.spdns.org/files/
 # http://hgm.nubati.net/cgi-bin/gitweb.cgi?p=xboard.git;a=snapshot;h=${COMMIT_HASH};sf=tgz
 # http://hgm.nubati.net/cgi-bin/gitweb.cgi/xboard.git/snapshot/${COMMIT_HASH}
Index: head/games/xboard/Makefile
===================================================================
--- head/games/xboard/Makefile
+++ head/games/xboard/Makefile
@@ -4,7 +4,7 @@
 PORTNAME?=	xboard
 PORTVERSION?=	4.9.1
 PORTREVISION?=	1
-PORTEPOCH?=
+PORTEPOCH?=	0
 CATEGORIES?=	games
 MASTER_SITES?=	GNU
 
Index: head/misc/dnetc/Makefile
===================================================================
--- head/misc/dnetc/Makefile
+++ head/misc/dnetc/Makefile
@@ -3,7 +3,7 @@
 
 PORTNAME=	dnetc
 PORTVERSION=	${VERSION}
-PORTREVISION=	${REVISION}
+PORTREVISION=	${REVISION:U0}
 PORTEPOCH=	1
 CATEGORIES=	misc
 MASTER_SITES=	http://http.distributed.net/pub/dcti/v${PORTVERSION:R}/ \
Index: head/www/mod_dav_svn/Makefile
===================================================================
--- head/www/mod_dav_svn/Makefile
+++ head/www/mod_dav_svn/Makefile
@@ -11,9 +11,6 @@
 
 USES=		apache:2.2+
 
-PORTREVISION_111=	1
-PORTREVISION_19=	0
-
 .include "${.CURDIR}/../../devel/subversion/Makefile.addons"
 
 CONFIGURE_ARGS+=	--with-apxs=${APXS} \
Index: head/www/nuvolaplayer-all-services/Makefile
===================================================================
--- head/www/nuvolaplayer-all-services/Makefile
+++ head/www/nuvolaplayer-all-services/Makefile
@@ -30,7 +30,7 @@
 NV_ID=		${${.CURDIR:T:S/${PORTNAME}-//}_ID}
 
 PORTVERSION=	${NV_${NV_ID}_VERSION}
-PORTREVISION?=	${NV_${NV_ID}_REVISION}
+PORTREVISION?=	${NV_${NV_ID}_REVISION:U0}
 PKGNAMESUFFIX?=	-${NV_${NV_ID}_NAME}
 
 COMMENT?=	${NV_${NV_ID}_DESC} integration for Nuvola Player