diff --git a/sim/src/mechanics/intersection.rs b/sim/src/mechanics/intersection.rs
index f6726f0df7..c410e0d1e7 100644
--- a/sim/src/mechanics/intersection.rs
+++ b/sim/src/mechanics/intersection.rs
@@ -156,8 +156,7 @@ impl IntersectionSimState {
                 }
             }
         } else {
-            return;
-            //unreachable!()
+            assert!(map.get_i(i).is_border());
         };
 
         for req in protected {