diff --git a/docs/Changelog.md b/docs/Changelog.md
index 77e583e..40470e2 100644
--- a/docs/Changelog.md
+++ b/docs/Changelog.md
@@ -127,3 +127,13 @@
 
 * Fixed a wrong population delta value in the system resource aggregate.
 * Fixed invalid pop growth when a system with capacity 0 is somehow colonized.
+
+# v1.3.3 (2024-06-20)
+
+## Improvements
+
+* Creating a new game now pauses all other games of the same owner.
+
+## Documentation
+
+* Improved the `403 Forbidden` error documentation for updating a running game.
diff --git a/src/game-logic/game-logic.service.ts b/src/game-logic/game-logic.service.ts
index d4f5da3..334a6c6 100644
--- a/src/game-logic/game-logic.service.ts
+++ b/src/game-logic/game-logic.service.ts
@@ -13,6 +13,7 @@ import {notFound} from '@mean-stream/nestx';
 import {Game} from '../game/game.schema';
 import {HOMESYSTEM_BUILDINGS, HOMESYSTEM_DISTRICT_COUNT, HOMESYSTEM_DISTRICTS} from './constants';
 import {MemberService} from '../member/member.service';
+import {SYSTEM_UPGRADES} from './system-upgrade';
 
 @Injectable()
 export class GameLogicService {
diff --git a/src/game/game.controller.ts b/src/game/game.controller.ts
index bfa15e1..fbb28ae 100644
--- a/src/game/game.controller.ts
+++ b/src/game/game.controller.ts
@@ -74,8 +74,8 @@ export class GameController {
   @NotFound()
   @ApiOperation({description: 'Change a game as owner.'})
   @ApiOkResponse({type: Game})
-  @ApiConflictResponse({description: 'Game is already running.'})
-  @ApiForbiddenResponse({description: 'Attempt to change a game that the current user does not own.'})
+  @ApiConflictResponse({description: 'Cannot change a running game (only `speed` is allowed).'})
+  @ApiForbiddenResponse({description: 'Only the owner can change the game.'})
   @ApiQuery({
     name: 'tick',
     description: 'Advance the game by one period and run all empire and system calculations.',
@@ -92,8 +92,8 @@ export class GameController {
     if (!user._id.equals(existing.owner)) {
       throw new ForbiddenException('Only the owner can change the game.');
     }
-    if (existing.started && !(Object.keys(dto).length === 1 && dto.speed !== undefined)) {
-      throw new ConflictException('Cannot change a running game.');
+    if (existing.started && !(Object.keys(dto).every(key => key === 'speed'))) {
+      throw new ConflictException('Cannot change a running game (only `speed` is allowed).');
     }
     const update: UpdateQuery<Game> = dto;
     if (tick) {
diff --git a/src/game/game.handler.ts b/src/game/game.handler.ts
index 0e390b1..ff3669e 100644
--- a/src/game/game.handler.ts
+++ b/src/game/game.handler.ts
@@ -2,6 +2,7 @@ import {Injectable} from '@nestjs/common';
 import {OnEvent} from '@nestjs/event-emitter';
 import {User} from '../user/user.schema';
 import {GameService} from './game.service';
+import {Game} from './game.schema';
 
 @Injectable()
 export class GameHandler {
@@ -10,6 +11,14 @@ export class GameHandler {
   ) {
   }
 
+  /**
+   * When a game is created, pause all the other games owner by the same user.
+   */
+  @OnEvent('games.*.created')
+  async onGameCreated(game: Game): Promise<void> {
+    await this.gameService.updateMany({owner: game.owner}, {speed: 0});
+  }
+
   @OnEvent('users.*.deleted')
   async onUserDeleted(user: User): Promise<void> {
     await this.gameService.deleteMany({owner: user._id});
diff --git a/src/game/game.schema.ts b/src/game/game.schema.ts
index 45c322e..b76d369 100644
--- a/src/game/game.schema.ts
+++ b/src/game/game.schema.ts
@@ -84,7 +84,7 @@ export class Game extends GlobalSchema {
   @IsBoolean()
   started: boolean;
 
-  @Prop({default: 0})
+  @Prop({default: 0, index: 1})
   @ApiProperty({
     description: 'The speed of the game, interpreted by clients.',
     default: 0,