diff --git a/luarules/gadgets/scav_spawner_defense.lua b/luarules/gadgets/scav_spawner_defense.lua
index 11eec919d35..1935b9f4576 100644
--- a/luarules/gadgets/scav_spawner_defense.lua
+++ b/luarules/gadgets/scav_spawner_defense.lua
@@ -1199,7 +1199,7 @@ if gadgetHandler:IsSyncedCode() then
 					end
 					if mRandom() <= config.spawnChance and waveParameters.frontbusters.cooldown <= 0 then
 						local squad = squadSpawnOptions.frontbusters[math.random(1, #squadSpawnOptions.frontbusters)]
-						if squad and ((surface == "land" and squad.surface ~= "sea") or (surface == "sea" and squad.surface ~= "land")) then
+						if squad and squad.surface and ((surface == "land" and squad.surface ~= "sea") or (surface == "sea" and squad.surface ~= "land")) then
 							if mRandom() <= config.spawnChance and (not waveParameters.frontbusters.units[squad.name]) and squad.minAnger <= techAnger and squad.maxAnger >= techAnger and Spring.GetTeamUnitDefCount(scavTeamID, UnitDefNames[squad.name].id) < squad.maxAlive and waveParameters.frontbusters.unitCount == 0 then
 								for i = 1, math.ceil(squad.squadSize*config.spawnChance*((SetCount(humanTeams)*config.scavPerPlayerMultiplier)+(1-config.scavPerPlayerMultiplier))) do
 									waveParameters.frontbusters.units[squad.name] = true