diff --git a/Fuyu.Backend.Core/DTO/Accounts/Account.cs b/Fuyu.Backend.Core/DTO/Accounts/Account.cs
index eb7624c..519ccc7 100644
--- a/Fuyu.Backend.Core/DTO/Accounts/Account.cs
+++ b/Fuyu.Backend.Core/DTO/Accounts/Account.cs
@@ -16,6 +16,6 @@ public class Account
         public string Password;
 
         [DataMember]
-        public Dictionary<string, List<int>> Games;
+        public Dictionary<string, int?> Games;
     }
 }
\ No newline at end of file
diff --git a/Fuyu.Backend.Core/Services/AccountService.cs b/Fuyu.Backend.Core/Services/AccountService.cs
index b22efd7..88e6665 100644
--- a/Fuyu.Backend.Core/Services/AccountService.cs
+++ b/Fuyu.Backend.Core/Services/AccountService.cs
@@ -121,10 +121,10 @@ public static ERegisterStatus RegisterAccount(string username, string password)
                 Id = GetNewAccountId(),
                 Username = username.ToLowerInvariant(),
                 Password = password,
-                Games = new Dictionary<string, List<int>>()
+                Games = new Dictionary<string, int?>
                 {
-                    { "eft",   new List<int>() },
-                    { "arena", new List<int>() },
+                    { "eft", null },
+                    { "arena", null }
                 }
             };
 
@@ -137,6 +137,10 @@ public static ERegisterStatus RegisterAccount(string username, string password)
         public static ERegisterStatus RegisterGame(string sessionId, string game, string edition)
         {
             var account = CoreOrm.GetAccount(sessionId);
+            if (account.Games.TryGetValue(game, out var aid) && aid.HasValue)
+            {
+                return ERegisterStatus.AlreadyExists;
+            }
 
             string address;
 
@@ -170,7 +174,7 @@ public static ERegisterStatus RegisterGame(string sessionId, string game, string
                 var response = Json.Parse<FuyuGameRegisterResponse>(responseJson);
 
                 // set game account id
-                account.Games[game].Add(response.AccountId);
+                account.Games[game] = response.AccountId;
             }
 
             CoreOrm.SetOrAddAccount(account);
diff --git a/Fuyu.Tests.Backend.EFT/EndToEnd/BackendTest.cs b/Fuyu.Tests.Backend.EFT/EndToEnd/BackendTest.cs
index c423011..efbe359 100644
--- a/Fuyu.Tests.Backend.EFT/EndToEnd/BackendTest.cs
+++ b/Fuyu.Tests.Backend.EFT/EndToEnd/BackendTest.cs
@@ -39,7 +39,7 @@ public static void AssemblyInitialize(TestContext testContext)
             Fuyu.Backend.Core.Services.AccountService.RegisterAccount("test-username", "test-password");
             var coreSessionId = Fuyu.Backend.Core.Services.AccountService.LoginAccount("test-username", "test-password");
             Fuyu.Backend.Core.Services.AccountService.RegisterGame(coreSessionId, "eft", "unheard");
-            var eftAccountId = CoreOrm.GetAccount(coreSessionId).Games["eft"][0];
+            var eftAccountId = CoreOrm.GetAccount(coreSessionId).Games["eft"].Value;
             var eftSessionId = Fuyu.Backend.EFT.Services.AccountService.LoginAccount(eftAccountId);
 
             // create request clients