diff --git a/CHANGELOG.md b/CHANGELOG.md
index 62554a26..583052ea 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -50,6 +50,9 @@ This is the rolling changelog for TShock for Terraria. Use past tense when addin
   * `OnPlaceTileEntity`: The check was newly added.
   * `OnPlaceItemFrame`: The check was newly added.
   * `OnFoodPlatterTryPlacing`: The check was newly added.
+* Fixed errors on startup not being reported to console. (@bartico6)
+* The server now correctly disconnects players with missing groups instead of throwing an exception, stalling the connection (@bartico6)
+* The server now rejects login attempts from players who would end up with a missing group. (@bartico6)
 
 ## TShock 4.5.4
 * Fixed ridiculous typo in `GetDataHandlers` which caused TShock to read the wrong field in the packet for `usingBiomeTorches`. (@hakusaro, @Arthri)
diff --git a/TShockAPI/Commands.cs b/TShockAPI/Commands.cs
index 55d281c3..195ed2e2 100644
--- a/TShockAPI/Commands.cs
+++ b/TShockAPI/Commands.cs
@@ -832,10 +832,16 @@ namespace TShockAPI
 						(usingUUID && account.UUID == args.Player.UUID && !TShock.Config.Settings.DisableUUIDLogin &&
 						!String.IsNullOrWhiteSpace(args.Player.UUID)))
 				{
-					args.Player.PlayerData = TShock.CharacterDB.GetPlayerData(args.Player, account.ID);
-
 					var group = TShock.Groups.GetGroupByName(account.Group);
 
+					if (!TShock.Groups.AssertGroupValid(args.Player, group, false))
+					{
+						args.Player.SendErrorMessage("Login attempt failed - see the message above.");
+						return;
+					}
+
+					args.Player.PlayerData = TShock.CharacterDB.GetPlayerData(args.Player, account.ID);
+
 					args.Player.Group = group;
 					args.Player.tempGroup = null;
 					args.Player.Account = account;
diff --git a/TShockAPI/DB/GroupManager.cs b/TShockAPI/DB/GroupManager.cs
index 3bb50881..750dc7a2 100644
--- a/TShockAPI/DB/GroupManager.cs
+++ b/TShockAPI/DB/GroupManager.cs
@@ -200,6 +200,45 @@ namespace TShockAPI.DB
 			LoadPermisions();
 
 			Group.DefaultGroup = GetGroupByName(TShock.Config.Settings.DefaultGuestGroupName);
+
+			AssertCoreGroupsPresent();
+		}
+
+		internal void AssertCoreGroupsPresent()
+		{
+			if (!GroupExists(TShock.Config.Settings.DefaultGuestGroupName))
+			{
+				TShock.Log.ConsoleError("The guest group could not be found. This may indicate a typo in the configuration file, or that the group was renamed or deleted.");
+				throw new Exception("The guest group could not be found.");
+			}
+
+			if (!GroupExists(TShock.Config.Settings.DefaultRegistrationGroupName))
+			{
+				TShock.Log.ConsoleError("The default usergroup could not be found. This may indicate a typo in the configuration file, or that the group was renamed or deleted.");
+				throw new Exception("The default usergroup could not be found.");
+			}
+		}
+
+		/// <summary>
+		/// Asserts that the group reference can be safely assigned to the player object.
+		/// <para>If this assertion fails, and <paramref name="kick"/> is true, the player is disconnected. If <paramref name="kick"/> is false, the player will receive an error message.</para>
+		/// </summary>
+		/// <param name="player">The player in question</param>
+		/// <param name="group">The group we want to assign them</param>
+		/// <param name="kick">Whether or not failing this check disconnects the player.</param>
+		/// <returns></returns>
+		public bool AssertGroupValid(TSPlayer player, Group group, bool kick)
+		{
+			if (group == null)
+			{
+				if (kick)
+					player.Disconnect("Your account's group could not be loaded. Please contact server administrators about this.");
+				else
+					player.SendErrorMessage("Your account's group could not be loaded. Please contact server administrators about this.");
+				return false;
+			}
+
+			return true;
 		}
 
 		private void AddDefaultGroup(string name, string parent, string permissions)
diff --git a/TShockAPI/GetDataHandlers.cs b/TShockAPI/GetDataHandlers.cs
index 3bed28b2..2a0fbfe8 100644
--- a/TShockAPI/GetDataHandlers.cs
+++ b/TShockAPI/GetDataHandlers.cs
@@ -2456,10 +2456,13 @@ namespace TShockAPI
 						args.Player.State = 2;
 					NetMessage.SendData((int)PacketTypes.WorldInfo, args.Player.Index);
 
-					args.Player.PlayerData = TShock.CharacterDB.GetPlayerData(args.Player, account.ID);
-
 					var group = TShock.Groups.GetGroupByName(account.Group);
 
+					if (!TShock.Groups.AssertGroupValid(args.Player, group, true))
+						return true;
+
+					args.Player.PlayerData = TShock.CharacterDB.GetPlayerData(args.Player, account.ID);
+
 					args.Player.Group = group;
 					args.Player.tempGroup = null;
 					args.Player.Account = account;
@@ -3037,6 +3040,9 @@ namespace TShockAPI
 
 					var group = TShock.Groups.GetGroupByName(account.Group);
 
+					if (!TShock.Groups.AssertGroupValid(args.Player, group, true))
+						return true;
+
 					args.Player.Group = group;
 					args.Player.tempGroup = null;
 					args.Player.Account = account;
diff --git a/TShockAPI/TShock.cs b/TShockAPI/TShock.cs
index 16fc1cb9..958d6507 100644
--- a/TShockAPI/TShock.cs
+++ b/TShockAPI/TShock.cs
@@ -386,8 +386,8 @@ namespace TShockAPI
 			}
 			catch (Exception ex)
 			{
-				Log.Error("Fatal Startup Exception");
-				Log.Error(ex.ToString());
+				Log.ConsoleError("Fatal Startup Exception");
+				Log.ConsoleError(ex.ToString());
 				Environment.Exit(1);
 			}
 		}