diff --git a/wadsrc/static/zscript/actors/inventory/inv_misc.zs b/wadsrc/static/zscript/actors/inventory/inv_misc.zs
index 5fc4e3fe2..318d29491 100644
--- a/wadsrc/static/zscript/actors/inventory/inv_misc.zs
+++ b/wadsrc/static/zscript/actors/inventory/inv_misc.zs
@@ -33,6 +33,7 @@ class Key : Inventory
 	Default
 	{
 		+DONTGIB;		// Don't disappear due to a crusher
+		+INVENTORY.ISKEYITEM;
 		Inventory.InterHubAmount 0;
 		Inventory.PickupSound "misc/k_pkup";
 	}
@@ -59,28 +60,6 @@ class Key : Inventory
 		return false;
 	}
 
-	override void AttachToOwner(Actor other)
-	{
-		Super.AttachToOwner(other);
-
-		if (multiplayer && !deathmatch && sv_coopsharekeys)
-		{
-			for (int i = 0; i < MAXPLAYERS; i++)
-			{
-				if (playeringame[i])
-				{
-					let pmo = players[i].mo;
-
-					if (pmo == other)
-						continue;
-
-					if (!pmo.FindInventory(GetClass()))
-						pmo.GiveInventoryType(GetClass());
-				}
-			}
-		}
-	}
-
 	override bool ShouldStay ()
 	{
 		return !!multiplayer;
@@ -127,6 +106,7 @@ class PuzzleItem : Inventory
 	{
 		+NOGRAVITY
 		+INVENTORY.INVBAR
+		+INVENTORY.ISKEYITEM
 		Inventory.DefMaxAmount;
 		Inventory.UseSound "PuzzleSuccess";
 		Inventory.PickupSound "misc/i_pkup";
diff --git a/wadsrc/static/zscript/actors/inventory/inventory.zs b/wadsrc/static/zscript/actors/inventory/inventory.zs
index c5680e05e..4108650a4 100644
--- a/wadsrc/static/zscript/actors/inventory/inventory.zs
+++ b/wadsrc/static/zscript/actors/inventory/inventory.zs
@@ -10,6 +10,7 @@ class Inventory : Actor
 	const BLINKTHRESHOLD = (4*32);
 	const BONUSADD = 6;
 
+	private bool bSharingItem; // Currently being shared (avoid infinite recursions).
 	private bool pickedUp[MAXPLAYERS]; // If items are set to local, track who already picked it up.
 
 	deprecated("3.7") private int ItemFlags;
@@ -68,6 +69,7 @@ class Inventory : Actor
 	flagdef AlwaysPickup: ItemFlags, 23;
 	flagdef Unclearable: ItemFlags, 24;
 	flagdef NeverLocal: ItemFlags, 25;
+	flagdef IsKeyItem: ItemFlags, 26;
 
 	flagdef ForceRespawnInSurvival: none, 0;
 	flagdef PickupFlash: none, 6;
@@ -258,6 +260,43 @@ class Inventory : Actor
 		}
 	}
 
+	protected void ShareItemWithPlayers(Actor giver)
+	{
+		if (bSharingItem)
+			return;
+
+		class<Inventory> type = GetClass();
+		int skip = giver && giver.player ? giver.PlayerNumber() : -1;
+
+		for (int i; i < MAXPLAYERS; ++i)
+		{
+			if (!playerInGame[i] || i == skip)
+				continue;
+
+			let item = Inventory(Spawn(type));
+			if (!item)
+				continue;
+
+			item.bSharingItem = true;
+			if (!item.CallTryPickup(players[i].mo))
+			{
+				item.Destroy();
+				continue;
+			}
+			item.bSharingItem = false;
+
+			if (!bQuiet)
+			{
+				PlayPickupSound(players[i].mo);
+				if (!bNoScreenFlash && players[i].PlayerState != PST_DEAD)
+					players[i].BonusCount = BONUSADD;
+			}
+		}
+
+		if (!bQuiet && consoleplayer != skip)
+			PrintPickupMessage(true, PickupMessage());
+	}
+
 	//===========================================================================
 	//
 	// Inventory :: DoRespawn
@@ -650,6 +689,10 @@ class Inventory : Actor
 			}
 			// [AA] Let the toucher do something with the item they've just received:
 			toucher.HasReceived(self);
+
+			// If the item can be shared, make sure every player gets a copy.
+			if (multiplayer && !deathmatch && sv_coopsharekeys && bIsKeyItem)
+				ShareItemWithPlayers(toucher);
 		}
 		return res, toucher;
 	}