diff --git a/OpenRA.Game/GameRules/WeaponInfo.cs b/OpenRA.Game/GameRules/WeaponInfo.cs
index 019e869c8b..8eaed63881 100644
--- a/OpenRA.Game/GameRules/WeaponInfo.cs
+++ b/OpenRA.Game/GameRules/WeaponInfo.cs
@@ -48,12 +48,15 @@ namespace OpenRA.GameRules
 		[Desc("Whether we should prevent prone response for infantry.")]
 		public readonly bool PreventProne = false;
 
-		public float EffectivenessAgainst(Actor self)
+		public float EffectivenessAgainst(ActorInfo ai)
 		{
-			var health = self.Info.Traits.GetOrDefault<HealthInfo>();
-			if (health == null) return 0f;
-			var armor = self.Info.Traits.GetOrDefault<ArmorInfo>();
-			if (armor == null || armor.Type == null) return 1;
+			var health = ai.Traits.GetOrDefault<HealthInfo>();
+			if (health == null)
+				return 0f;
+
+			var armor = ai.Traits.GetOrDefault<ArmorInfo>();
+			if (armor == null || armor.Type == null)
+				return 1;
 
 			float versus;
 			return Versus.TryGetValue(armor.Type, out versus) ? versus : 1;
@@ -140,7 +143,7 @@ namespace OpenRA.GameRules
 			if (targetable == null || !ValidTargets.Intersect(targetable.TargetTypes).Any())
 				return false;
 
-			if (Warheads.All(w => w.EffectivenessAgainst(a) <= 0))
+			if (Warheads.All(w => w.EffectivenessAgainst(a.Info) <= 0))
 				return false;
 
 			return true;
diff --git a/OpenRA.Mods.RA/Combat.cs b/OpenRA.Mods.RA/Combat.cs
index 37b751f09f..c50613a2a0 100755
--- a/OpenRA.Mods.RA/Combat.cs
+++ b/OpenRA.Mods.RA/Combat.cs
@@ -118,7 +118,7 @@ namespace OpenRA.Mods.RA
 						foreach (var t in world.FindTilesInCircle(targetTile, warhead.Size[0]))
 							foreach (var unit in world.FindActorsInBox(t, t))
 								unit.InflictDamage(firedBy,
-									(int)(warhead.Damage * warhead.EffectivenessAgainst(unit)), warhead);
+									(int)(warhead.Damage * warhead.EffectivenessAgainst(unit.Info)), warhead);
 					} break;
 			}
 		}
@@ -173,7 +173,7 @@ namespace OpenRA.Mods.RA
 			var distance = (int)Math.Max(0, (target.CenterPosition - pos).Length * Game.CellSize / 1024 - health.Radius);
 			var falloff = (float)GetDamageFalloff(distance / warhead.Spread);
 			var rawDamage = (float)(warhead.Damage * modifier * falloff);
-			var multiplier = (float)warhead.EffectivenessAgainst(target);
+			var multiplier = (float)warhead.EffectivenessAgainst(target.Info);
 
 			return (float)(rawDamage * multiplier);
 		}