diff --git a/wadsrc/static/actors/actor.txt b/wadsrc/static/actors/actor.txt
index 7faf389e78..fcc8d5ded7 100644
--- a/wadsrc/static/actors/actor.txt
+++ b/wadsrc/static/actors/actor.txt
@@ -298,23 +298,23 @@ ACTOR Actor native //: Thinker
 	action native A_SetDamageType(name damagetype);
 	action native A_DropItem(class<Actor> item, int dropamount = -1, int chance = 256);
 	action native A_SetSpeed(float speed);
-	action native A_DamageSelf(int amount, name damagetype = "none", int flags = 0, class<Actor> filter, name species);
-	action native A_DamageTarget(int amount, name damagetype = "none", int flags = 0, class<Actor> filter, name species);
-	action native A_DamageMaster(int amount, name damagetype = "none", int flags = 0, class<Actor> filter, name species);
-	action native A_DamageTracer(int amount, name damagetype = "none", int flags = 0, class<Actor> filter, name species);
-	action native A_DamageChildren(int amount, name damagetype = "none", int flags = 0, class<Actor> filter, name species);
-	action native A_DamageSiblings(int amount, name damagetype = "none", int flags = 0, class<Actor> filter, name species);
-	action native A_KillTarget(name damagetype = "none", int flags = 0, class<Actor> filter, name species);
-	action native A_KillMaster(name damagetype = "none", int flags = 0, class<Actor> filter, name species);
-	action native A_KillTracer(name damagetype = "none", int flags = 0, class<Actor> filter, name species);
-	action native A_KillChildren(name damagetype = "none", int flags = 0, class<Actor> filter, name species);
-	action native A_KillSiblings(name damagetype = "none", int flags = 0, class<Actor> filter, name species);
-	action native A_RemoveTarget(int flags = 0, class<Actor> filter, name species);
-	action native A_RemoveMaster(int flags = 0, class<Actor> filter, name species);
-	action native A_RemoveTracer(int flags = 0, class<Actor> filter, name species);
-	action native A_RemoveChildren(bool removeall = false, int flags = 0, class<Actor> filter, name species);
-	action native A_RemoveSiblings(bool removeall = false, int flags = 0, class<Actor> filter, name species);
-	action native A_Remove(int removee, int flags = 0, class<Actor> filter, name species);
+	action native A_DamageSelf(int amount, name damagetype = "none", int flags = 0, class<Actor> filter = "None", name species);
+	action native A_DamageTarget(int amount, name damagetype = "none", int flags = 0, class<Actor> filter = "None", name species);
+	action native A_DamageMaster(int amount, name damagetype = "none", int flags = 0, class<Actor> filter = "None", name species);
+	action native A_DamageTracer(int amount, name damagetype = "none", int flags = 0, class<Actor> filter = "None", name species);
+	action native A_DamageChildren(int amount, name damagetype = "none", int flags = 0, class<Actor> filter = "None", name species);
+	action native A_DamageSiblings(int amount, name damagetype = "none", int flags = 0, class<Actor> filter = "None", name species);
+	action native A_KillTarget(name damagetype = "none", int flags = 0, class<Actor> filter = "None", name species);
+	action native A_KillMaster(name damagetype = "none", int flags = 0, class<Actor> filter = "None", name species);
+	action native A_KillTracer(name damagetype = "none", int flags = 0, class<Actor> filter = "None", name species);
+	action native A_KillChildren(name damagetype = "none", int flags = 0, class<Actor> filter = "None", name species);
+	action native A_KillSiblings(name damagetype = "none", int flags = 0, class<Actor> filter = "None", name species);
+	action native A_RemoveTarget(int flags = 0, class<Actor> filter = "None", name species);
+	action native A_RemoveMaster(int flags = 0, class<Actor> filter = "None", name species);
+	action native A_RemoveTracer(int flags = 0, class<Actor> filter = "None", name species);
+	action native A_RemoveChildren(bool removeall = false, int flags = 0, class<Actor> filter = "None", name species);
+	action native A_RemoveSiblings(bool removeall = false, int flags = 0, class<Actor> filter = "None", name species);
+	action native A_Remove(int removee, int flags = 0, class<Actor> filter = "None", name species);
 	action native A_GiveToChildren(class<Inventory> itemtype, int amount = 0);
 	action native A_GiveToSiblings(class<Inventory> itemtype, int amount = 0);
 	action native A_TakeFromChildren(class<Inventory> itemtype, int amount = 0);