diff --git a/usr.sbin/bsdinstall/Makefile b/usr.sbin/bsdinstall/Makefile
--- a/usr.sbin/bsdinstall/Makefile
+++ b/usr.sbin/bsdinstall/Makefile
@@ -22,8 +22,11 @@
 
 .if ${BRANCH} == CURRENT || ${BRANCH} == STABLE
 SUBURL=		base_latest
-.else
+.elif ${BRANCH} == RELEASE
 SUBURL=		base_release_${REVISION:C/[0-9]+\.//}
+.else
+.warning Invalid branch "${BRANCH}"
+SUBURL=		base_latest
 .endif
 
 FreeBSD-base.conf: FreeBSD-base.conf.in