diff --git a/maps/crab_defender/main.lua b/maps/crab_defender/main.lua
index c9c48855f..21ac04efa 100644
--- a/maps/crab_defender/main.lua
+++ b/maps/crab_defender/main.lua
@@ -1125,17 +1125,17 @@ local function deny_building(event)
     return false
 end
 
-local on_built_entity = function(event)
+local on_built_entity = function (event)
     local get_score = Score.get_table().score_table
     local this = FDT.get()
     local entity = event.created_entity
-    local surface = entity.surface
 
-    if not surface or not surface.valid then
+    if not entity or not entity.valid then
         return
     end
+    local surface = entity.surface
 
-    if not entity.valid then
+    if not surface or not surface.valid then
         return
     end