diff --git a/PluralKit.Bot/CommandSystem/Context.cs b/PluralKit.Bot/CommandSystem/Context.cs
index 61ae35b1..2502e317 100644
--- a/PluralKit.Bot/CommandSystem/Context.cs
+++ b/PluralKit.Bot/CommandSystem/Context.cs
@@ -276,7 +276,7 @@ namespace PluralKit.Bot
         public LookupContext LookupContextFor(PKSystem target) => 
             System?.Id == target.Id ? LookupContext.ByOwner : LookupContext.ByNonOwner;
         
-        public LookupContext LookupContextFor(int systemId) => 
+        public LookupContext LookupContextFor(SystemId systemId) => 
             System?.Id == systemId ? LookupContext.ByOwner : LookupContext.ByNonOwner;
 
         public Context CheckSystemPrivacy(PKSystem target, PrivacyLevel level)
diff --git a/PluralKit.Bot/Commands/Autoproxy.cs b/PluralKit.Bot/Commands/Autoproxy.cs
index 3f871829..1c875ec1 100644
--- a/PluralKit.Bot/Commands/Autoproxy.cs
+++ b/PluralKit.Bot/Commands/Autoproxy.cs
@@ -87,7 +87,7 @@ namespace PluralKit.Bot
             var fronters = ctx.MessageContext.LastSwitchMembers;
             var relevantMember = ctx.MessageContext.AutoproxyMode switch
             {
-                AutoproxyMode.Front => fronters.Count > 0 ? await _db.Execute(c => c.QueryMember(fronters[0])) : null,
+                AutoproxyMode.Front => fronters.Length > 0 ? await _db.Execute(c => c.QueryMember(fronters[0])) : null,
                 AutoproxyMode.Member => await _db.Execute(c => c.QueryMember(ctx.MessageContext.AutoproxyMember.Value)),
                 _ => null
             };
@@ -97,7 +97,7 @@ namespace PluralKit.Bot
                     break;
                 case AutoproxyMode.Front:
                 {
-                    if (fronters.Count == 0)
+                    if (fronters.Length == 0)
                         eb.WithDescription("Autoproxy is currently set to **front mode** in this server, but there are currently no fronters registered. Use the `pk;switch` command to log a switch.");
                     else
                     {
@@ -123,7 +123,7 @@ namespace PluralKit.Bot
             return eb.Build();
         }
         
-        private Task UpdateAutoproxy(Context ctx, AutoproxyMode autoproxyMode, int? autoproxyMember) =>
+        private Task UpdateAutoproxy(Context ctx, AutoproxyMode autoproxyMode, MemberId? autoproxyMember) =>
             _db.Execute(c => 
                 c.ExecuteAsync(
                     "update system_guild set autoproxy_mode = @autoproxyMode, autoproxy_member = @autoproxyMember where guild = @guild and system = @system",
diff --git a/PluralKit.Bot/Proxy/ProxyMatcher.cs b/PluralKit.Bot/Proxy/ProxyMatcher.cs
index d4f81081..5dcfbdc9 100644
--- a/PluralKit.Bot/Proxy/ProxyMatcher.cs
+++ b/PluralKit.Bot/Proxy/ProxyMatcher.cs
@@ -48,7 +48,7 @@ namespace PluralKit.Bot
                 AutoproxyMode.Member when ctx.AutoproxyMember != null => 
                     members.FirstOrDefault(m => m.Id == ctx.AutoproxyMember),
                 
-                AutoproxyMode.Front when ctx.LastSwitchMembers.Count > 0 => 
+                AutoproxyMode.Front when ctx.LastSwitchMembers.Length > 0 => 
                     members.FirstOrDefault(m => m.Id == ctx.LastSwitchMembers[0]),
                 
                 AutoproxyMode.Latch when ctx.LastMessageMember != null && !IsLatchExpired(ctx.LastMessage) =>
diff --git a/PluralKit.Core/Database/Database.cs b/PluralKit.Core/Database/Database.cs
index 85aac202..b010df62 100644
--- a/PluralKit.Core/Database/Database.cs
+++ b/PluralKit.Core/Database/Database.cs
@@ -1,6 +1,8 @@
 using System;
+using System.Collections.Generic;
 using System.Data;
 using System.IO;
+using System.Linq;
 using System.Threading.Tasks;
 
 using App.Metrics;
@@ -36,13 +38,14 @@ namespace PluralKit.Core
         
         public static void InitStatic()
         {
+            DefaultTypeMap.MatchNamesWithUnderscores = true;
+            
             // Dapper by default tries to pass ulongs to Npgsql, which rejects them since PostgreSQL technically
             // doesn't support unsigned types on its own.
             // Instead we add a custom mapper to encode them as signed integers instead, converting them back and forth.
             SqlMapper.RemoveTypeMap(typeof(ulong));
             SqlMapper.AddTypeHandler(new UlongEncodeAsLongHandler());
             SqlMapper.AddTypeHandler(new UlongArrayHandler());
-            DefaultTypeMap.MatchNamesWithUnderscores = true;
 
             NpgsqlConnection.GlobalTypeMapper.UseNodaTime();
             // With the thing we add above, Npgsql already handles NodaTime integration
@@ -51,6 +54,14 @@ namespace PluralKit.Core
             SqlMapper.AddTypeHandler(new PassthroughTypeHandler<Instant>());
             SqlMapper.AddTypeHandler(new PassthroughTypeHandler<LocalDate>());
             
+            // Add ID types to Dapper
+            SqlMapper.AddTypeHandler(new NumericIdHandler<SystemId, int>(i => new SystemId(i)));
+            SqlMapper.AddTypeHandler(new NumericIdHandler<MemberId, int>(i => new MemberId(i)));
+            SqlMapper.AddTypeHandler(new NumericIdHandler<SwitchId, int>(i => new SwitchId(i)));
+            SqlMapper.AddTypeHandler(new NumericIdArrayHandler<SystemId, int>(i => new SystemId(i)));
+            SqlMapper.AddTypeHandler(new NumericIdArrayHandler<MemberId, int>(i => new MemberId(i)));
+            SqlMapper.AddTypeHandler(new NumericIdArrayHandler<SwitchId, int>(i => new SwitchId(i)));
+            
             // Register our custom types to Npgsql
             // Without these it'll still *work* but break at the first launch + probably cause other small issues
             NpgsqlConnection.GlobalTypeMapper.MapComposite<ProxyTag>("proxy_tag");
@@ -153,5 +164,37 @@ namespace PluralKit.Core
 
             public override ulong[] Parse(object value) => Array.ConvertAll((long[]) value, i => (ulong) i);
         }
+
+        private class NumericIdHandler<T, TInner>: SqlMapper.TypeHandler<T>
+            where T: INumericId<T, TInner>
+            where TInner: IEquatable<TInner>, IComparable<TInner>
+        {
+            private readonly Func<TInner, T> _factory;
+
+            public NumericIdHandler(Func<TInner, T> factory)
+            {
+                _factory = factory;
+            }
+
+            public override void SetValue(IDbDataParameter parameter, T value) => parameter.Value = value.Value;
+
+            public override T Parse(object value) => _factory((TInner) value);
+        }
+
+        private class NumericIdArrayHandler<T, TInner>: SqlMapper.TypeHandler<T[]>
+            where T: INumericId<T, TInner>
+            where TInner: IEquatable<TInner>, IComparable<TInner>
+        {
+            private readonly Func<TInner, T> _factory;
+
+            public NumericIdArrayHandler(Func<TInner, T> factory)
+            {
+                _factory = factory;
+            }
+
+            public override void SetValue(IDbDataParameter parameter, T[] value) => parameter.Value = Array.ConvertAll(value, v => v.Value);
+
+            public override T[] Parse(object value) => Array.ConvertAll((TInner[]) value, v => _factory(v));
+        }
     }
 }
\ No newline at end of file
diff --git a/PluralKit.Core/Database/Functions/MessageContext.cs b/PluralKit.Core/Database/Functions/MessageContext.cs
index 369479f7..4de64d2c 100644
--- a/PluralKit.Core/Database/Functions/MessageContext.cs
+++ b/PluralKit.Core/Database/Functions/MessageContext.cs
@@ -10,18 +10,18 @@ namespace PluralKit.Core
     /// </summary>
     public class MessageContext
     {
-        public int? SystemId { get; }
+        public SystemId? SystemId { get; }
         public ulong? LogChannel { get; }
         public bool InBlacklist { get; }
         public bool InLogBlacklist { get; }
         public bool LogCleanupEnabled { get; }
         public bool ProxyEnabled { get; }
         public AutoproxyMode AutoproxyMode { get; }
-        public int? AutoproxyMember { get; }
+        public MemberId? AutoproxyMember { get; }
         public ulong? LastMessage { get; }
-        public int? LastMessageMember { get; }
-        public int LastSwitch { get; }
-        public IReadOnlyList<int> LastSwitchMembers { get; } = new int[0];
+        public MemberId? LastMessageMember { get; }
+        public SwitchId LastSwitch { get; }
+        public MemberId[] LastSwitchMembers { get; } = new MemberId[0];
         public Instant LastSwitchTimestamp { get; }
         public string? SystemTag { get; }
         public string? SystemAvatar { get; }
diff --git a/PluralKit.Core/Database/Functions/ProxyMember.cs b/PluralKit.Core/Database/Functions/ProxyMember.cs
index d57480af..96becdde 100644
--- a/PluralKit.Core/Database/Functions/ProxyMember.cs
+++ b/PluralKit.Core/Database/Functions/ProxyMember.cs
@@ -8,7 +8,7 @@ namespace PluralKit.Core
     /// </summary>
     public class ProxyMember
     {
-        public int Id { get; }
+        public MemberId Id { get; }
         public IReadOnlyCollection<ProxyTag> ProxyTags { get; } = new ProxyTag[0];
         public bool KeepProxy { get; }
         
diff --git a/PluralKit.Core/Database/Views/DatabaseViewsExt.cs b/PluralKit.Core/Database/Views/DatabaseViewsExt.cs
index 2f156472..b62637af5 100644
--- a/PluralKit.Core/Database/Views/DatabaseViewsExt.cs
+++ b/PluralKit.Core/Database/Views/DatabaseViewsExt.cs
@@ -9,10 +9,10 @@ namespace PluralKit.Core
 {
     public static class DatabaseViewsExt
     {
-        public static Task<IEnumerable<SystemFronter>> QueryCurrentFronters(this IPKConnection conn, int system) =>
+        public static Task<IEnumerable<SystemFronter>> QueryCurrentFronters(this IPKConnection conn, SystemId system) =>
             conn.QueryAsync<SystemFronter>("select * from system_fronters where system = @system", new {system});
 
-        public static Task<IEnumerable<ListedMember>> QueryMemberList(this IPKConnection conn, int system, PrivacyLevel? privacyFilter = null, string? filter = null, bool includeDescriptionInNameFilter = false)
+        public static Task<IEnumerable<ListedMember>> QueryMemberList(this IPKConnection conn, SystemId system, PrivacyLevel? privacyFilter = null, string? filter = null, bool includeDescriptionInNameFilter = false)
         {
             StringBuilder query = new StringBuilder("select * from member_list where system = @system");
 
diff --git a/PluralKit.Core/Database/Views/SystemFronter.cs b/PluralKit.Core/Database/Views/SystemFronter.cs
index c727dc22..4983b720 100644
--- a/PluralKit.Core/Database/Views/SystemFronter.cs
+++ b/PluralKit.Core/Database/Views/SystemFronter.cs
@@ -4,10 +4,10 @@ namespace PluralKit.Core
 {
     public class SystemFronter
     {
-        public int SystemId { get; }
-        public int SwitchId { get; }
+        public SystemId SystemId { get; }
+        public SwitchId SwitchId { get; }
         public Instant SwitchTimestamp { get; }
-        public int MemberId { get; }
+        public MemberId MemberId { get; }
         public string MemberHid { get; }
         public string MemberName { get; }
     }
diff --git a/PluralKit.Core/Models/INumericId.cs b/PluralKit.Core/Models/INumericId.cs
new file mode 100644
index 00000000..25d1eac5
--- /dev/null
+++ b/PluralKit.Core/Models/INumericId.cs
@@ -0,0 +1,11 @@
+using System;
+
+namespace PluralKit.Core
+{
+    public interface INumericId<T, out TInner>: IEquatable<T>, IComparable<T>
+        where T: INumericId<T, TInner>
+        where TInner: IEquatable<TInner>, IComparable<TInner>
+    {
+        public TInner Value { get; }
+    }
+}
\ No newline at end of file
diff --git a/PluralKit.Core/Models/MemberGuildSettings.cs b/PluralKit.Core/Models/MemberGuildSettings.cs
index 2729f0f2..7a3102cb 100644
--- a/PluralKit.Core/Models/MemberGuildSettings.cs
+++ b/PluralKit.Core/Models/MemberGuildSettings.cs
@@ -3,7 +3,7 @@ namespace PluralKit.Core
 {
     public class MemberGuildSettings
     {
-        public int Member { get; }
+        public MemberId Member { get; }
         public ulong Guild { get; }
         public string? DisplayName { get; }
         public string? AvatarUrl { get; }
diff --git a/PluralKit.Core/Models/MemberId.cs b/PluralKit.Core/Models/MemberId.cs
new file mode 100644
index 00000000..2fa90ba6
--- /dev/null
+++ b/PluralKit.Core/Models/MemberId.cs
@@ -0,0 +1,24 @@
+namespace PluralKit.Core
+{
+    public readonly struct MemberId: INumericId<MemberId, int>
+    {
+        public int Value { get; }
+
+        public MemberId(int value)
+        {
+            Value = value;
+        }
+
+        public bool Equals(MemberId other) => Value == other.Value;
+
+        public override bool Equals(object obj) => obj is MemberId other && Equals(other);
+
+        public override int GetHashCode() => Value;
+
+        public static bool operator ==(MemberId left, MemberId right) => left.Equals(right);
+
+        public static bool operator !=(MemberId left, MemberId right) => !left.Equals(right);
+
+        public int CompareTo(MemberId other) => Value.CompareTo(other.Value);
+    }
+}
\ No newline at end of file
diff --git a/PluralKit.Core/Models/ModelQueryExt.cs b/PluralKit.Core/Models/ModelQueryExt.cs
index e91f41c4..e4d7fa5f 100644
--- a/PluralKit.Core/Models/ModelQueryExt.cs
+++ b/PluralKit.Core/Models/ModelQueryExt.cs
@@ -7,22 +7,22 @@ namespace PluralKit.Core
 {
     public static class ModelQueryExt
     {
-        public static Task<PKSystem?> QuerySystem(this IPKConnection conn, int id) =>
+        public static Task<PKSystem?> QuerySystem(this IPKConnection conn, SystemId id) =>
             conn.QueryFirstOrDefaultAsync<PKSystem?>("select * from systems where id = @id", new {id});
         
-        public static Task<PKMember?> QueryMember(this IPKConnection conn, int id) =>
+        public static Task<PKMember?> QueryMember(this IPKConnection conn, MemberId id) =>
             conn.QueryFirstOrDefaultAsync<PKMember?>("select * from members where id = @id", new {id});
         
         public static Task<GuildConfig> QueryOrInsertGuildConfig(this IPKConnection conn, ulong guild) =>
             conn.QueryFirstAsync<GuildConfig>("insert into servers (id) values (@guild) on conflict (id) do update set id = @guild returning *", new {guild});
 
-        public static Task<SystemGuildSettings> QueryOrInsertSystemGuildConfig(this IPKConnection conn, ulong guild, int system) =>
+        public static Task<SystemGuildSettings> QueryOrInsertSystemGuildConfig(this IPKConnection conn, ulong guild, SystemId system) =>
             conn.QueryFirstAsync<SystemGuildSettings>(
                 "insert into member_guild (guild, member) values (@guild, @member) on conflict (guild, member) do update set guild = @guild, member = @member returning *", 
                 new {guild, system});
 
         public static Task<MemberGuildSettings> QueryOrInsertMemberGuildConfig(
-            this IPKConnection conn, ulong guild, int member) =>
+            this IPKConnection conn, ulong guild, MemberId member) =>
             conn.QueryFirstAsync<MemberGuildSettings>(
                 "insert into member_guild (guild, member) values (@guild, @member) on conflict (guild, member) do update set guild = @guild, member = @member returning *",
                 new {guild, member});
diff --git a/PluralKit.Core/Models/PKMember.cs b/PluralKit.Core/Models/PKMember.cs
index 73b5d551..c13c9c05 100644
--- a/PluralKit.Core/Models/PKMember.cs
+++ b/PluralKit.Core/Models/PKMember.cs
@@ -8,9 +8,9 @@ using NodaTime.Text;
 namespace PluralKit.Core {
     public class PKMember
     {
-        public int Id { get; }
+        public MemberId Id { get; }
         public string Hid { get; set; }
-        public int System { get; set; }
+        public SystemId System { get; set; }
         public string Color { get; set; }
         public string AvatarUrl { get; set; }
         public string Name { get; set; }
diff --git a/PluralKit.Core/Models/PKSwitch.cs b/PluralKit.Core/Models/PKSwitch.cs
index b8057a3c..0ac4be40 100644
--- a/PluralKit.Core/Models/PKSwitch.cs
+++ b/PluralKit.Core/Models/PKSwitch.cs
@@ -3,8 +3,8 @@
 namespace PluralKit.Core {
     public class PKSwitch
     {
-        public int Id { get; }
-        public int System { get; set; }
+        public SwitchId Id { get; }
+        public SystemId System { get; set; }
         public Instant Timestamp { get; }
     }
 }
\ No newline at end of file
diff --git a/PluralKit.Core/Models/PKSystem.cs b/PluralKit.Core/Models/PKSystem.cs
index c47234ce..73d457a4 100644
--- a/PluralKit.Core/Models/PKSystem.cs
+++ b/PluralKit.Core/Models/PKSystem.cs
@@ -8,7 +8,7 @@ namespace PluralKit.Core {
     public class PKSystem
     {
         // Additions here should be mirrored in SystemStore::Save
-        [Key] public int Id { get; }
+        [Key] public SystemId Id { get; }
         public string Hid { get; }
         public string Name { get; set; }
         public string Description { get; set; }
diff --git a/PluralKit.Core/Models/SwitchId.cs b/PluralKit.Core/Models/SwitchId.cs
new file mode 100644
index 00000000..11a775a0
--- /dev/null
+++ b/PluralKit.Core/Models/SwitchId.cs
@@ -0,0 +1,24 @@
+namespace PluralKit.Core
+{
+    public readonly struct SwitchId: INumericId<SwitchId, int>
+    {
+        public int Value { get; }
+
+        public SwitchId(int value)
+        {
+            Value = value;
+        }
+
+        public bool Equals(SwitchId other) => Value == other.Value;
+
+        public override bool Equals(object obj) => obj is SwitchId other && Equals(other);
+
+        public override int GetHashCode() => Value;
+
+        public static bool operator ==(SwitchId left, SwitchId right) => left.Equals(right);
+
+        public static bool operator !=(SwitchId left, SwitchId right) => !left.Equals(right);
+
+        public int CompareTo(SwitchId other) => Value.CompareTo(other.Value);
+    }
+}
\ No newline at end of file
diff --git a/PluralKit.Core/Models/SystemGuildSettings.cs b/PluralKit.Core/Models/SystemGuildSettings.cs
index 770b50b2..88afed36 100644
--- a/PluralKit.Core/Models/SystemGuildSettings.cs
+++ b/PluralKit.Core/Models/SystemGuildSettings.cs
@@ -2,10 +2,10 @@
 {
     public class SystemGuildSettings
     {
-        public ulong Guild { get; }
+        public SystemId Guild { get; }
         public bool ProxyEnabled { get; } = true;
 
         public AutoproxyMode AutoproxyMode { get; } = AutoproxyMode.Off;
-        public int? AutoproxyMember { get; }
+        public MemberId? AutoproxyMember { get; }
     }
 }
\ No newline at end of file
diff --git a/PluralKit.Core/Models/SystemId.cs b/PluralKit.Core/Models/SystemId.cs
new file mode 100644
index 00000000..42c1336a
--- /dev/null
+++ b/PluralKit.Core/Models/SystemId.cs
@@ -0,0 +1,24 @@
+namespace PluralKit.Core
+{
+    public readonly struct SystemId: INumericId<SystemId, int>
+    {
+        public int Value { get; }
+
+        public SystemId(int value)
+        {
+            Value = value;
+        }
+
+        public bool Equals(SystemId other) => Value == other.Value;
+
+        public override bool Equals(object obj) => obj is SystemId other && Equals(other);
+
+        public override int GetHashCode() => Value;
+
+        public static bool operator ==(SystemId left, SystemId right) => left.Equals(right);
+
+        public static bool operator !=(SystemId left, SystemId right) => !left.Equals(right);
+
+        public int CompareTo(SystemId other) => Value.CompareTo(other.Value);
+    }
+}
\ No newline at end of file
diff --git a/PluralKit.Core/Services/IDataStore.cs b/PluralKit.Core/Services/IDataStore.cs
index d3d3b141..f6493465 100644
--- a/PluralKit.Core/Services/IDataStore.cs
+++ b/PluralKit.Core/Services/IDataStore.cs
@@ -45,7 +45,7 @@ namespace PluralKit.Core {
     
     public struct SwitchMembersListEntry
     {
-        public int Member;
+        public MemberId Member;
         public Instant Timestamp;
     }
 
@@ -131,7 +131,7 @@ namespace PluralKit.Core {
         /// Gets a system by its internal member ID.
         /// </summary>
         /// <returns>The <see cref="PKMember"/> with the given internal ID, or null if no member was found.</returns>
-        Task<PKMember> GetMemberById(int memberId);
+        Task<PKMember> GetMemberById(MemberId memberId);
         
         /// <summary>
         /// Gets a member by its user-facing human ID.
@@ -195,7 +195,7 @@ namespace PluralKit.Core {
         /// <param name="triggerMessageId">The ID of the original trigger message containing the proxy tags.</param>
         /// <param name="proxiedMemberId">The member (and by extension system) that was proxied.</param>
         /// <returns></returns>
-        Task AddMessage(IPKConnection conn, ulong senderAccount, ulong guildId, ulong channelId, ulong postedMessageId, ulong triggerMessageId, int proxiedMemberId);
+        Task AddMessage(IPKConnection conn, ulong senderAccount, ulong guildId, ulong channelId, ulong postedMessageId, ulong triggerMessageId, MemberId proxiedMemberId);
         
         /// <summary>
         /// Deletes a message from the data store.
diff --git a/PluralKit.Core/Services/PostgresDataStore.cs b/PluralKit.Core/Services/PostgresDataStore.cs
index a9c57dc6..4579f012 100644
--- a/PluralKit.Core/Services/PostgresDataStore.cs
+++ b/PluralKit.Core/Services/PostgresDataStore.cs
@@ -125,7 +125,7 @@ namespace PluralKit.Core {
             return member;
         }
 
-        public async Task<PKMember> GetMemberById(int id) {
+        public async Task<PKMember> GetMemberById(MemberId id) {
             using (var conn = await _conn.Obtain())
                 return await conn.QuerySingleOrDefaultAsync<PKMember>("select * from members where id = @Id", new { Id = id });
         }
@@ -177,7 +177,7 @@ namespace PluralKit.Core {
                 return await conn.ExecuteScalarAsync<ulong>("select count(id) from members");
         }
         
-        public async Task AddMessage(IPKConnection conn, ulong senderId, ulong guildId, ulong channelId, ulong postedMessageId, ulong triggerMessageId, int proxiedMemberId) {
+        public async Task AddMessage(IPKConnection conn, ulong senderId, ulong guildId, ulong channelId, ulong postedMessageId, ulong triggerMessageId, MemberId proxiedMemberId) {
             // "on conflict do nothing" in the (pretty rare) case of duplicate events coming in from Discord, which would lead to a DB error before
             await conn.ExecuteAsync("insert into messages(mid, guild, channel, member, sender, original_mid) values(@MessageId, @GuildId, @ChannelId, @MemberId, @SenderId, @OriginalMid) on conflict do nothing", new {
                 MessageId = postedMessageId,
@@ -334,7 +334,7 @@ namespace PluralKit.Core {
             // query DB for all members involved in any of the switches above and collect into a dictionary for future use
             // this makes sure the return list has the same instances of PKMember throughout, which is important for the dictionary
             // key used in GetPerMemberSwitchDuration below
-            Dictionary<int, PKMember> memberObjects;
+            Dictionary<MemberId, PKMember> memberObjects;
             using (var conn = await _conn.Obtain())
             {
                 memberObjects = (
@@ -351,7 +351,7 @@ namespace PluralKit.Core {
                 select new SwitchListEntry
                 {
                     TimespanStart = g.Key,
-                    Members = g.Where(x => x.Member != 0).Select(x => memberObjects[x.Member]).ToList()
+                    Members = g.Where(x => x.Member != default(MemberId)).Select(x => memberObjects[x.Member]).ToList()
                 };
 
             // Loop through every switch that overlaps the range and add it to the output list
diff --git a/PluralKit.Core/Utils/BulkImporter.cs b/PluralKit.Core/Utils/BulkImporter.cs
index cd7b848f..4defb17a 100644
--- a/PluralKit.Core/Utils/BulkImporter.cs
+++ b/PluralKit.Core/Utils/BulkImporter.cs
@@ -16,14 +16,14 @@ namespace PluralKit.Core
 {
     public class BulkImporter: IAsyncDisposable
     {
-        private readonly int _systemId;
+        private readonly SystemId _systemId;
         private readonly IPKConnection _conn;
         private readonly IPKTransaction _tx;
-        private readonly Dictionary<string, int> _knownMembers = new Dictionary<string, int>();
+        private readonly Dictionary<string, MemberId> _knownMembers = new Dictionary<string, MemberId>();
         private readonly Dictionary<string, PKMember> _existingMembersByHid = new Dictionary<string, PKMember>();
         private readonly Dictionary<string, PKMember> _existingMembersByName = new Dictionary<string, PKMember>();
 
-        private BulkImporter(int systemId, IPKConnection conn, IPKTransaction tx)
+        private BulkImporter(SystemId systemId, IPKConnection conn, IPKTransaction tx)
         {
             _systemId = systemId;
             _conn = conn;
@@ -124,7 +124,7 @@ namespace PluralKit.Core
             // Fetch the existing switches in the database so we can avoid duplicates
             var existingSwitches = (await _conn.QueryAsync<PKSwitch>("select * from switches where system = @System", new {System = _systemId})).ToList();
             var existingTimestamps = existingSwitches.Select(sw => sw.Timestamp).ToImmutableHashSet();
-            var lastSwitchId = existingSwitches.Count != 0 ? existingSwitches.Select(sw => sw.Id).Max() : -1;
+            var lastSwitchId = existingSwitches.Count != 0 ? existingSwitches.Select(sw => sw.Id).Max() : (SwitchId?) null;
 
             // Import switch definitions
             var importedSwitches = new Dictionary<Instant, SwitchInfo>();
@@ -152,7 +152,7 @@ namespace PluralKit.Core
             // IDs are sequential, so any ID in this system, with a switch ID > the last max, will be one we just added
             var justAddedSwitches = await _conn.QueryAsync<PKSwitch>(
                 "select * from switches where system = @System and id > @LastSwitchId",
-                new {System = _systemId, LastSwitchId = lastSwitchId});
+                new {System = _systemId, LastSwitchId = lastSwitchId?.Value ?? -1});
             
             // Lastly, import the switch members
             await using (var importer = _conn.BeginBinaryImport("copy switch_members (switch, member) from stdin (format binary)"))