diff --git a/src/commands/add-inventory-command.ts b/src/commands/add-inventory-command.ts
index c1ed204..a237201 100644
--- a/src/commands/add-inventory-command.ts
+++ b/src/commands/add-inventory-command.ts
@@ -4,7 +4,7 @@ import { Command } from './command';
 import { EventPublisher } from '../domain/event-publisher';
 import { Voice } from '../domain/voice';
 import { ItemFormatter } from './item-formatter';
-import { GameState } from '../state/game-state';
+import { ReadOnlyGameState } from '../state/game-state';
 
 /** Class representing a command instructing the game to add a list of item deltas to inventory.
  * Item deltas consist of an item and a count.
@@ -44,10 +44,8 @@ export class AddInventoryCommand implements Command {
     }
   }
 
-  execute(gameState: GameState, publisher: EventPublisher): void {
+  execute(gameState: ReadOnlyGameState, publisher: EventPublisher): void {
     for (const delta of this.deltas) {
-      gameState.addInventory(delta.item, delta.count);
-
       publisher.publish({
         topic: 'player.inventory.added',
         message: `You add ${ItemFormatter.formatProseItem(delta.item, delta.count)} to your pack.`,
diff --git a/src/commands/command.ts b/src/commands/command.ts
index 52b8841..bfa92a0 100644
--- a/src/commands/command.ts
+++ b/src/commands/command.ts
@@ -1,8 +1,8 @@
 'use strict';
 
-import { GameState } from '../state/game-state';
+import { ReadOnlyGameState } from '../state/game-state';
 import { EventPublisher } from '../domain/event-publisher';
 
 export interface Command {
-  execute(gameState: GameState, publisher: EventPublisher): void;
+  execute(gameState: ReadOnlyGameState, publisher: EventPublisher): void;
 }
diff --git a/src/domain/game-state-event-subscriber.ts b/src/domain/game-state-event-subscriber.ts
index 2881be6..65ed574 100644
--- a/src/domain/game-state-event-subscriber.ts
+++ b/src/domain/game-state-event-subscriber.ts
@@ -12,6 +12,9 @@ export class GameStateEventSubscriber implements EventSubscriber {
       case 'player.location.moved':
         this.gameState.setCurrentLocation(this.map.get(event.currentNode.id));
         break;
+      case 'player.inventory.added':
+        this.gameState.addInventory(event.item, event.count);
+        break;
     }
   }
 }
diff --git a/src/test/commands/add-inventory.spec.ts b/src/test/commands/add-inventory.spec.ts
index 77ff3ee..3e91970 100644
--- a/src/test/commands/add-inventory.spec.ts
+++ b/src/test/commands/add-inventory.spec.ts
@@ -58,12 +58,6 @@ describe('AddInventoryCommand', () => {
         command = new AddInventoryCommand(deltas);
       });
 
-      it('Should call gs.addinventory once.', () => {
-        command.execute(gameState, publisher);
-
-        mockito.verify(GameStateMock.addInventory(item, 1)).once();
-      });
-
       it('Should call publisher.publish once.', () => {
         command.execute(gameState, publisher);
 
@@ -88,12 +82,6 @@ describe('AddInventoryCommand', () => {
         command = new AddInventoryCommand(deltas, true);
       });
 
-      it('Should call gs.addinventory once.', () => {
-        command.execute(gameState, publisher);
-
-        mockito.verify(GameStateMock.addInventory(item, 1)).once();
-      });
-
       it('Should call publisher.publish once with mute voice.', () => {
         command.execute(gameState, publisher);
 
@@ -116,13 +104,6 @@ describe('AddInventoryCommand', () => {
         command = new AddInventoryCommand(deltas);
       });
 
-      it('Should call gs.addinventory twice.', () => {
-        command.execute(gameState, publisher);
-
-        mockito.verify(GameStateMock.addInventory(item1, 5)).once();
-        mockito.verify(GameStateMock.addInventory(item2, 5)).once();
-      });
-
       it('Should call publisher.publish twice.', () => {
         command.execute(gameState, publisher);
 
@@ -154,12 +135,6 @@ describe('AddInventoryCommand', () => {
         command = new AddInventoryCommand(deltas);
       });
 
-      it('Should call gs.addinventory once with 0 as count.', () => {
-        command.execute(gameState, publisher);
-
-        mockito.verify(GameStateMock.addInventory(item, 0)).once();
-      });
-
       it('Should call publisher.publish once.', () => {
         command.execute(gameState, publisher);
 
@@ -183,12 +158,6 @@ describe('AddInventoryCommand', () => {
         command.addDelta(item, 1);
       });
 
-      it('Should call gs.addinventory once.', () => {
-        command.execute(gameState, publisher);
-
-        mockito.verify(GameStateMock.addInventory(item, 1)).once();
-      });
-
       it('Should call publisher.publish once.', () => {
         command.execute(gameState, publisher);