1 files changed, 1 insertions, 1 deletions

diff --git a/rules.js b/rules.js
index 64c2a23..73a5cc3 100644
--- a/rules.js
+++ b/rules.js
@@ -3339,7 +3339,7 @@ function search_supply_by_way(result, start, carts, ships) {
         let dist = search_dist[here];
         let next_dist = dist + 8;
         if (can_supply_at(here, ships)) {
-            if (result)
+            if (Array.isArray(result))
                 map_set(result, here, dist);
             else
                 return true;