diff --git a/src/geometry.F90 b/src/geometry.F90
index 0bacd7b5d..e747b619a 100644
--- a/src/geometry.F90
+++ b/src/geometry.F90
@@ -355,9 +355,10 @@ contains
             else
               ! Particle is outside the lattice.
               if (lat % outer == NO_OUTER_UNIVERSE) then
-                call p % mark_as_lost("Particle " // trim(to_str(p %id)) &
+                call warning("Particle " // trim(to_str(p %id)) &
                      // " is outside lattice " // trim(to_str(lat % id)) &
                      // " but the lattice has no defined outer universe.")
+                found = .false.
                 return
               else
                 p % coord(j + 1) % universe = lat % outer