Juniper is somewhat (in-)famous for unhelpful and/or superfluous error messages. We faced a new one on our Juniper MX boxes recently. A normal-looking static route was committed, the next-hop was reachable via an irb interface bound to a VPLS instance:
[edit routing-options static]
+ route 10.1.2.168/29 {
+ next-hop 10.1.2.167;
+ tag 666;
+ }