diff --git a/Mk/tree.mk b/Mk/tree.mk
index e74e960cb..c3bd2ebf1 100644
--- a/Mk/tree.mk
+++ b/Mk/tree.mk
@@ -1,7 +1,5 @@
 all:
 
-ROOT?=	/usr/local
-
 .for TARGET in ${TREES} ${EXTRAS}
 
 .if "${TREES_${TARGET}}" == ""
@@ -9,6 +7,9 @@ TREES_${TARGET}=${TARGET}
 .endif
 
 .if "${ROOT_${TARGET}}" == ""
+.if "${ROOT}" == ""
+.error "No ROOT directory set for target: ${TARGET}"
+.endif
 ROOT_${TARGET}=${ROOT}
 .endif
 
diff --git a/src/Makefile b/src/Makefile
index 22cbfcfff..418fb093d 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -1,4 +1,5 @@
 TREES=		boot etc opnsense sbin wizard www
+ROOT=		/usr/local
 ROOT_boot=	/
 
 EXTRAS=		bootstrap