diff --git a/wadsrc/static/zscript/inventory/ammo.txt b/wadsrc/static/zscript/inventory/ammo.txt
index cc97611e0..52b3d8f22 100644
--- a/wadsrc/static/zscript/inventory/ammo.txt
+++ b/wadsrc/static/zscript/inventory/ammo.txt
@@ -249,11 +249,10 @@ class BackpackItem : Inventory
 		uint end = AllActorClasses.Size();
 		for (uint i = 0; i < end; ++i)
 		{
-			let type = AllActorClasses[i];
+			let ammotype = (class<Ammo>)(AllActorClasses[i]);
 
-			if (type.GetParentClass() == 'Ammo')
+			if (ammotype && GetDefaultByType(ammotype).GetParentAmmo() == ammotype)
 			{
-				let ammotype = (class<Ammo>)(type);
 				let ammoitem = Ammo(other.FindInventory(ammotype));
 				int amount = GetDefaultByType(ammotype).BackpackAmount;
 				// extra ammo in baby mode and nightmare mode
@@ -314,20 +313,22 @@ class BackpackItem : Inventory
 		{
 			for (let probe = Owner.Inv; probe != NULL; probe = probe.Inv)
 			{
-				if (probe.GetParentClass() == 'Ammo')
+				let ammoitem = Ammo(probe);
+
+				if (ammoitem && ammoitem.GetParentAmmo() == ammoitem.GetClass())
 				{
-					if (probe.Amount < probe.MaxAmount || sv_unlimited_pickup)
+					if (ammoitem.Amount < ammoitem.MaxAmount || sv_unlimited_pickup)
 					{
-						int amount = Ammo(probe).Default.BackpackAmount;
+						int amount = ammoitem.Default.BackpackAmount;
 						// extra ammo in baby mode and nightmare mode
 						if (!bIgnoreSkill)
 						{
 							amount = int(amount * G_SkillPropertyFloat(SKILLP_AmmoFactor));
 						}
-						probe.Amount += amount;
-						if (probe.Amount > probe.MaxAmount && !sv_unlimited_pickup)
+						ammoitem.Amount += amount;
+						if (ammoitem.Amount > ammoitem.MaxAmount && !sv_unlimited_pickup)
 						{
-							probe.Amount = probe.MaxAmount;
+							ammoitem.Amount = ammoitem.MaxAmount;
 						}
 					}
 				}
diff --git a/wadsrc/static/zscript/shared/player_cheat.txt b/wadsrc/static/zscript/shared/player_cheat.txt
index 8bd9d34c2..506a60480 100644
--- a/wadsrc/static/zscript/shared/player_cheat.txt
+++ b/wadsrc/static/zscript/shared/player_cheat.txt
@@ -99,14 +99,14 @@ extend class PlayerPawn
 			// he doesn't have it already, and set each to its maximum.
 			for (i = 0; i < AllActorClasses.Size(); ++i)
 			{
-				type = (class<Inventory>)(AllActorClasses[i]);
+				let ammotype = (class<Ammo>)(AllActorClasses[i]);
 
-				if (type != null && type.GetParentClass() == "Ammo")
+				if (ammotype && GetDefaultByType(ammotype).GetParentAmmo() == ammotype)
 				{
-					let ammoitem = FindInventory(type);
+					let ammoitem = FindInventory(ammotype);
 					if (ammoitem == NULL)
 					{
-						ammoitem = Inventory(Spawn (type));
+						ammoitem = Inventory(Spawn (ammotype));
 						ammoitem.AttachToOwner (self);
 						ammoitem.Amount = ammoitem.MaxAmount;
 					}