diff --git a/sys/conf/kern.opts.mk b/sys/conf/kern.opts.mk
index b3ce90eaf223..6ce98917e410 100644
--- a/sys/conf/kern.opts.mk
+++ b/sys/conf/kern.opts.mk
@@ -21,4 +21,15 @@ __DEFAULT_YES_OPTIONS = \
 
 __DEFAULT_NO_OPTIONS = \
 
+# Kludge to allow a less painful transition. If MAKESYSPATH isn't defined,
+# assume we have a standard FreeBSD src tree layout and reach over and grab
+# bsd.mkopt.mk from there. If it is defined, trust it to point someplace sane
+# and include bsd.mkopt.mk from there. We need the !defined case to keep ports
+# kernel modules working (though arguably they should define MAKESYSPATH). We
+# need the latter case to keep the JIRA case working where they specifically
+# use a non-standard layout, but do define MAKESYSPATH correctly.
+.if !defined(MAKESYSPATH)
 .include "../../share/mk/bsd.mkopt.mk"
+.else
+.include <bsd.mkopt.mk>
+.endif