Cannot deserialize inherited members with aggregation queries (fluent API)

Given class hierarchy:

    public class Aggregate : Entity
    {
        public string Id { get; set; }
    }

    public class Entity
    {
        public IEnumerable<LocalizableText> Name { get; set; }
    }

    public class Branch : Aggregate
    {
        public IEnumerable<LocalizableText> Description { get; set; }
        public string PartnerId { get; set; }
        public double Latitude { get; set; }
        public double Longitude { get; set; }
        public string Timetable { get; set; }
        public IEnumerable<Discount> Discounts { get; set; }
        public IEnumerable<Category> Categories { get; set; }
        public IEnumerable<Phone> Phones { get; set; }
        public byte[] Icon { get; set; }
        public byte[] Image { get; set; }
    }

Given mappings:

            BsonClassMap.RegisterClassMap<Entity>(cm =>
            {
                cm.SetIsRootClass(true);
                cm.MapProperty(e => e.Name);
                cm.SetDiscriminator(typeof(Entity).Name);
                cm.AddKnownType(typeof(Aggregate));
                cm.AddKnownType(typeof(Branch));
                
            });
            BsonClassMap.RegisterClassMap<Aggregate>(cm =>
            {
                cm.SetIsRootClass(true);
                cm.SetDiscriminator(typeof(Aggregate).Name);
                cm.SetIdMember(cm.GetMemberMap(a => a.Id));
                cm.AddKnownType(typeof(Branch));
            });
           BsonClassMap.RegisterClassMap<Branch>(cm =>
            {
                cm.AutoMap();
                cm.SetDiscriminator(typeof(Branch).Name);
            });

When running the query:

        public async Task<Branch> GetBranchToolTipAsync(string partnerId, string branchId)
        {
            return await Collection.Aggregate()
                .Match(x => x.PartnerId == partnerId)
                .Group(x => x.PartnerId, g => new Branch()
                {
                    PartnerId = g.Key,
                    Name = g.First(x => x.PartnerId == partnerId).Name,
                    Description = g.First(x => x.Id == branchId).Name,
                    Discounts = g.First(x => x.Id == branchId).Discounts,
                    Id = branchId
                }).FirstOrDefaultAsync();
        }

Then the following exception occurs:

Test method Server.Application.Tests.Services.Partners.PartnerApplicationServiceTests.ShouldGetBranchToolTipAsync threw exception: 

System.ArgumentOutOfRangeException: The memberInfo argument must be for class Branch, but was for class Entity.

Parameter name: memberInfo
    at MongoDB.Bson.Serialization.BsonClassMap.EnsureMemberInfoIsForThisClass(MemberInfo memberInfo)
   at MongoDB.Bson.Serialization.BsonClassMap.MapMember(MemberInfo memberInfo)
   at MongoDB.Driver.Linq.Translators.AggregateProjectionTranslator.SerializerBuilder.BuildProjectedSerializer(ProjectionMapping mapping)
   at MongoDB.Driver.Linq.Translators.AggregateProjectionTranslator.SerializerBuilder.BuildMemberInit(MemberInitExpression node)
   at MongoDB.Driver.Linq.Translators.AggregateProjectionTranslator.SerializerBuilder.Build(Expression node)
   at MongoDB.Driver.Linq.Translators.AggregateProjectionTranslator.SerializerBuilder.Build(Expression node, IBsonSerializerRegistry serializerRegistry)
   at MongoDB.Driver.Linq.Translators.AggregateProjectionTranslator.TranslateGroup(Expression`1 idProjector, Expression`1 groupProjector, IBsonSerializer`1 parameterSerializer, IBsonSerializerRegistry serializerRegistry)
   at MongoDB.Driver.IAggregateFluentExtensions.GroupExpressionProjection`3.Render(IBsonSerializer`1 documentSerializer, IBsonSerializerRegistry serializerRegistry)
   at MongoDB.Driver.AggregateFluent`2.<>c__DisplayClass1`1.<Group>b__0(IBsonSerializer`1 s, IBsonSerializerRegistry sr)
   at MongoDB.Driver.DelegatedPipelineStageDefinition`2.Render(IBsonSerializer`1 inputSerializer, IBsonSerializerRegistry serializerRegistry)
   at MongoDB.Driver.PipelineStageDefinition`2.MongoDB.Driver.IPipelineStageDefinition.Render(IBsonSerializer inputSerializer, IBsonSerializerRegistry serializerRegistry)
   at MongoDB.Driver.PipelineStagePipelineDefinition`2.Render(IBsonSerializer`1 inputSerializer, IBsonSerializerRegistry serializerRegistry)
   at MongoDB.Driver.MongoCollectionImpl`1.<AggregateAsync>d__7`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.ConfiguredTaskAwaitable`1.ConfiguredTaskAwaiter.GetResult()
   at MongoDB.Driver.IAggregateFluentExtensions.<FirstOrDefaultAsync>d__b`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
   at SCNDISC.Server.Infrastructure.Persistence.Queries.Partners.BranchToolTipQuery.<GetBranchToolTipAsync>d__2.MoveNext() in BranchToolTipQuery.cs: line 16
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
   at SCNDISC.Server.Application.Services.Partners.PartnerApplicationService.<GetBranchToolTipAsync>d__9.MoveNext() in PartnerApplicationService.cs: line 46
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
   at SCNDISC.Server.Application.Tests.Services.Partners.PartnerApplicationServiceTests.<ShouldGetBranchToolTipAsync>d__35.MoveNext() in PartnerApplicationServiceTests.cs: line 87
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.GetResult()