diff --git a/Mk/Uses/uniquefiles.mk b/Mk/Uses/uniquefiles.mk
--- a/Mk/Uses/uniquefiles.mk
+++ b/Mk/Uses/uniquefiles.mk
@@ -83,11 +83,11 @@
 UNIQUE_SUFFIX_TYPES+=	SUFFIX
 
 .  if ${uniquefiles_ARGS:Mdirs}
-DOCSDIR=	${PREFIX}/share/doc/${UNIQUE_PREFIX}${PORTNAME}
-EXAMPLESDIR=	${PREFIX}/share/examples/${UNIQUE_PREFIX}${PORTNAME}
-DATADIR=	${PREFIX}/share/${UNIQUE_PREFIX}${PORTNAME}
-WWWDIR=		${PREFIX}/www/${UNIQUE_PREFIX}${PORTNAME}
-ETCDIR=		${PREFIX}/etc/${UNIQUE_PREFIX}${PORTNAME}
+DOCSDIR?=	${PREFIX}/share/doc/${UNIQUE_PREFIX}${PORTNAME}
+EXAMPLESDIR?=	${PREFIX}/share/examples/${UNIQUE_PREFIX}${PORTNAME}
+DATADIR?=	${PREFIX}/share/${UNIQUE_PREFIX}${PORTNAME}
+WWWDIR?=	${PREFIX}/www/${UNIQUE_PREFIX}${PORTNAME}
+ETCDIR?=	${PREFIX}/etc/${UNIQUE_PREFIX}${PORTNAME}
 .  endif
 
 UNIQUE_DEFAULT_LINKS?=		no